1. 10 Nov, 2015 2 commits
  2. 06 Nov, 2015 28 commits
    • Kirill A. Shutemov's avatar
      mm: use 'unsigned int' for page order · d00181b9
      Kirill A. Shutemov authored
      Let's try to be consistent about data type of page order.
      
      [sfr@canb.auug.org.au: fix build (type of pageblock_order)]
      [hughd@google.com: some configs end up with MAX_ORDER and pageblock_order having different types]
      Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Reviewed-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
      Cc: Andi Kleen <ak@linux.intel.com>
      Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Signed-off-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
      Signed-off-by: default avatarHugh Dickins <hughd@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d00181b9
    • Kirill A. Shutemov's avatar
      mm: make compound_head() robust · 1d798ca3
      Kirill A. Shutemov authored
      Hugh has pointed that compound_head() call can be unsafe in some
      context. There's one example:
      
      	CPU0					CPU1
      
      isolate_migratepages_block()
        page_count()
          compound_head()
            !!PageTail() == true
      					put_page()
      					  tail->first_page = NULL
            head = tail->first_page
      					alloc_pages(__GFP_COMP)
      					   prep_compound_page()
      					     tail->first_page = head
      					     __SetPageTail(p);
            !!PageTail() == true
          <head == NULL dereferencing>
      
      The race is pure theoretical. I don't it's possible to trigger it in
      practice. But who knows.
      
      We can fix the race by changing how encode PageTail() and compound_head()
      within struct page to be able to update them in one shot.
      
      The patch introduces page->compound_head into third double word block in
      front of compound_dtor and compound_order. Bit 0 encodes PageTail() and
      the rest bits are pointer to head page if bit zero is set.
      
      The patch moves page->pmd_huge_pte out of word, just in case if an
      architecture defines pgtable_t into something what can have the bit 0
      set.
      
      hugetlb_cgroup uses page->lru.next in the second tail page to store
      pointer struct hugetlb_cgroup. The patch switch it to use page->private
      in the second tail page instead. The space is free since ->first_page is
      removed from the union.
      
      The patch also opens possibility to remove HUGETLB_CGROUP_MIN_ORDER
      limitation, since there's now space in first tail page to store struct
      hugetlb_cgroup pointer. But that's out of scope of the patch.
      
      That means page->compound_head shares storage space with:
      
       - page->lru.next;
       - page->next;
       - page->rcu_head.next;
      
      That's too long list to be absolutely sure, but looks like nobody uses
      bit 0 of the word.
      
      page->rcu_head.next guaranteed[1] to have bit 0 clean as long as we use
      call_rcu(), call_rcu_bh(), call_rcu_sched(), or call_srcu(). But future
      call_rcu_lazy() is not allowed as it makes use of the bit and we can
      get false positive PageTail().
      
      [1] http://lkml.kernel.org/g/20150827163634.GD4029@linux.vnet.ibm.comSigned-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Reviewed-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Vlastimil Babka <vbabka@suse.cz>
      Acked-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
      Cc: Andi Kleen <ak@linux.intel.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      1d798ca3
    • Kirill A. Shutemov's avatar
      mm: pack compound_dtor and compound_order into one word in struct page · f1e61557
      Kirill A. Shutemov authored
      The patch halves space occupied by compound_dtor and compound_order in
      struct page.
      
      For compound_order, it's trivial long -> short conversion.
      
      For get_compound_page_dtor(), we now use hardcoded table for destructor
      lookup and store its index in the struct page instead of direct pointer
      to destructor. It shouldn't be a big trouble to maintain the table: we
      have only two destructor and NULL currently.
      
      This patch free up one word in tail pages for reuse. This is preparation
      for the next patch.
      Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Reviewed-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Reviewed-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
      Cc: Andi Kleen <ak@linux.intel.com>
      Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      f1e61557
    • Kirill A. Shutemov's avatar
      zsmalloc: use page->private instead of page->first_page · 32e7ba1e
      Kirill A. Shutemov authored
      We are going to rework how compound_head() work. It will not use
      page->first_page as we have it now.
      
      The only other user of page->first_page beyond compound pages is
      zsmalloc.
      
      Let's use page->private instead of page->first_page here. It occupies
      the same storage space.
      Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Reviewed-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Reviewed-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
      Cc: Andi Kleen <ak@linux.intel.com>
      Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Michal Hocko <mhocko@suse.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      32e7ba1e
    • Kirill A. Shutemov's avatar
      slab, slub: use page->rcu_head instead of page->lru plus cast · bc4f610d
      Kirill A. Shutemov authored
      We have properly typed page->rcu_head, no need to cast page->lru.
      Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Reviewed-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarChristoph Lameter <cl@linux.com>
      Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
      Cc: Andi Kleen <ak@linux.intel.com>
      Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Michal Hocko <mhocko@suse.com>
      Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Cc: Vlastimil Babka <vbabka@suse.cz>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      bc4f610d
    • Sergey Senozhatsky's avatar
      zsmalloc: reduce size_class memory usage · 6fe5186f
      Sergey Senozhatsky authored
      Each `struct size_class' contains `struct zs_size_stat': an array of
      NR_ZS_STAT_TYPE `unsigned long'.  For zsmalloc built with no
      CONFIG_ZSMALLOC_STAT this results in a waste of `2 * sizeof(unsigned
      long)' per-class.
      
      The patch removes unneeded `struct zs_size_stat' members by redefining
      NR_ZS_STAT_TYPE (max stat idx in array).
      
      Since both NR_ZS_STAT_TYPE and zs_stat_type are compile time constants,
      GCC can eliminate zs_stat_inc()/zs_stat_dec() calls that use zs_stat_type
      larger than NR_ZS_STAT_TYPE: CLASS_ALMOST_EMPTY and CLASS_ALMOST_FULL at
      the moment.
      
      ./scripts/bloat-o-meter mm/zsmalloc.o.old mm/zsmalloc.o.new
      add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-39 (-39)
      function                                     old     new   delta
      fix_fullness_group                            97      94      -3
      insert_zspage                                100      86     -14
      remove_zspage                                141     119     -22
      
      To summarize:
      a) each class now uses less memory
      b) we avoid a number of dec/inc stats (a minor optimization,
         but still).
      
      The gain will increase once we introduce additional stats.
      
      A simple IO test.
      
      iozone -t 4 -R -r 32K -s 60M -I +Z
                              patched                 base
      "  Initial write "       4145599.06              4127509.75
      "        Rewrite "       4146225.94              4223618.50
      "           Read "      17157606.00             17211329.50
      "        Re-read "      17380428.00             17267650.50
      "   Reverse Read "      16742768.00             16162732.75
      "    Stride read "      16586245.75             16073934.25
      "    Random read "      16349587.50             15799401.75
      " Mixed workload "      10344230.62              9775551.50
      "   Random write "       4277700.62              4260019.69
      "         Pwrite "       4302049.12              4313703.88
      "          Pread "       6164463.16              6126536.72
      "         Fwrite "       7131195.00              6952586.00
      "          Fread "      12682602.25             12619207.50
      Signed-off-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Cc: Minchan Kim <minchan@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      6fe5186f
    • Hui Zhu's avatar
      mm/zsmalloc.c: remove useless line in obj_free() · 6f0b2276
      Hui Zhu authored
      Signed-off-by: default avatarHui Zhu <zhuhui@xiaomi.com>
      Reviewed-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Cc: Minchan Kim <minchan@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      6f0b2276
    • Sergey Senozhatsky's avatar
      zsmalloc: don't test shrinker_enabled in zs_shrinker_count() · 2c351695
      Sergey Senozhatsky authored
      We don't let user to disable shrinker in zsmalloc (once it's been
      enabled), so no need to check ->shrinker_enabled in zs_shrinker_count(),
      at the moment at least.
      Signed-off-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Acked-by: default avatarMinchan Kim <minchan@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      2c351695
    • Sergey Senozhatsky's avatar
      zsmalloc: use preempt.h for in_interrupt() · 759b26b2
      Sergey Senozhatsky authored
      A cosmetic change.
      
      Commit c60369f0 ("staging: zsmalloc: prevent mappping in interrupt
      context") added in_interrupt() check to zs_map_object() and 'hardirq.h'
      include; but in_interrupt() macro is defined in 'preempt.h' not in
      'hardirq.h', so include it instead.
      Signed-off-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Acked-by: default avatarMinchan Kim <minchan@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      759b26b2
    • Hui Zhu's avatar
      zsmalloc: fix obj_to_head use page_private(page) as value but not pointer · 12a7bfad
      Hui Zhu authored
      In obj_malloc():
      
      	if (!class->huge)
      		/* record handle in the header of allocated chunk */
      		link->handle = handle;
      	else
      		/* record handle in first_page->private */
      		set_page_private(first_page, handle);
      
      In the hugepage we save handle to private directly.
      
      But in obj_to_head():
      
      	if (class->huge) {
      		VM_BUG_ON(!is_first_page(page));
      		return *(unsigned long *)page_private(page);
      	} else
      		return *(unsigned long *)obj;
      
      It is used as a pointer.
      
      The reason why there is no problem until now is huge-class page is born
      with ZS_FULL so it can't be migrated.  However, we need this patch for
      future work: "VM-aware zsmalloced page migration" to reduce external
      fragmentation.
      Signed-off-by: default avatarHui Zhu <zhuhui@xiaomi.com>
      Acked-by: default avatarMinchan Kim <minchan@kernel.org>
      Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      12a7bfad
    • Hui Zhu's avatar
      zsmalloc: add comments for ->inuse to zspage · 8f958c98
      Hui Zhu authored
      [akpm@linux-foundation.org: fix grammar]
      Signed-off-by: default avatarHui Zhu <zhuhui@xiaomi.com>
      Reviewed-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Cc: Dan Streetman <ddstreet@ieee.org>
      Cc: Minchan Kim <minchan@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      8f958c98
    • Sergey SENOZHATSKY's avatar
      mm: zsmalloc: constify struct zs_pool name · 6f3526d6
      Sergey SENOZHATSKY authored
      Constify `struct zs_pool' ->name.
      
      [akpm@inux-foundation.org: constify zpool_create_pool()'s `type' arg also]
      Signed-off-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Acked-by: default avatarDan Streetman <ddstreet@ieee.org>
      Cc: Minchan Kim <minchan@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      6f3526d6
    • Dan Streetman's avatar
      zpool: remove redundant zpool->type string, const-ify zpool_get_type · 69e18f4d
      Dan Streetman authored
      Make the return type of zpool_get_type const; the string belongs to the
      zpool driver and should not be modified.  Remove the redundant type field
      in the struct zpool; it is private to zpool.c and isn't needed since
      ->driver->type can be used directly.  Add comments indicating strings must
      be null-terminated.
      Signed-off-by: default avatarDan Streetman <ddstreet@ieee.org>
      Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Cc: Seth Jennings <sjennings@variantweb.net>
      Cc: Minchan Kim <minchan@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      69e18f4d
    • Dan Streetman's avatar
      zswap: use charp for zswap param strings · c99b42c3
      Dan Streetman authored
      Instead of using a fixed-length string for the zswap params, use charp.
      This simplifies the code and uses less memory, as most zswap param strings
      will be less than the current maximum length.
      Signed-off-by: default avatarDan Streetman <ddstreet@ieee.org>
      Cc: Rusty Russell <rusty@rustcorp.com.au>
      Cc: Seth Jennings <sjennings@variantweb.net>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      c99b42c3
    • Alexey Klimov's avatar
      mm/zswap.c: remove unneeded initialization to NULL in zswap_entry_find_get() · b0c9865f
      Alexey Klimov authored
      On the next line entry variable will be re-initialized so no need to init
      it with NULL.
      Signed-off-by: default avatarAlexey Klimov <alexey.klimov@linaro.org>
      Cc: Seth Jennings <sjennings@variantweb.net>
      Cc: Dan Streetman <ddstreet@ieee.org>
      Cc: Minchan Kim <minchan@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      b0c9865f
    • Andrew Morton's avatar
      mm/memcontrol.c: uninline mem_cgroup_usage · 6f646156
      Andrew Morton authored
      gcc version 5.2.1 20151010 (Debian 5.2.1-22)
      $ size mm/memcontrol.o mm/memcontrol.o.before
         text    data     bss     dec     hex filename
        35535    7908      64   43507    a9f3 mm/memcontrol.o
        35762    7908      64   43734    aad6 mm/memcontrol.o.before
      
      Cc: Michal Hocko <mhocko@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      6f646156
    • Aaron Tomlin's avatar
      thp: remove unused vma parameter from khugepaged_alloc_page · d6669d68
      Aaron Tomlin authored
      The "vma" parameter to khugepaged_alloc_page() is unused.  It has to
      remain unused or the drop read lock 'map_sem' optimisation introduce by
      commit 8b164568 ("mm, THP: don't hold mmap_sem in khugepaged when
      allocating THP") wouldn't be safe.  So let's remove it.
      Signed-off-by: default avatarAaron Tomlin <atomlin@redhat.com>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d6669d68
    • Michal Hocko's avatar
      mm, fs: introduce mapping_gfp_constraint() · c62d2555
      Michal Hocko authored
      There are many places which use mapping_gfp_mask to restrict a more
      generic gfp mask which would be used for allocations which are not
      directly related to the page cache but they are performed in the same
      context.
      
      Let's introduce a helper function which makes the restriction explicit and
      easier to track.  This patch doesn't introduce any functional changes.
      
      [akpm@linux-foundation.org: coding-style fixes]
      Signed-off-by: default avatarMichal Hocko <mhocko@suse.com>
      Suggested-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      c62d2555
    • Mel Gorman's avatar
      mm: page_alloc: hide some GFP internals and document the bits and flag combinations · dd56b046
      Mel Gorman authored
      Andrew stated the following
      
      	We have quite a history of remote parts of the kernel using
      	weird/wrong/inexplicable combinations of __GFP_ flags.	I tend
      	to think that this is because we didn't adequately explain the
      	interface.
      
      	And I don't think that gfp.h really improved much in this area as
      	a result of this patchset.  Could you go through it some time and
      	decide if we've adequately documented all this stuff?
      
      This patches first moves some GFP flag combinations that are part of the MM
      internals to mm/internal.h. The rest of the patch documents the __GFP_FOO
      bits under various headings and then documents the flag combinations. It
      will not help callers that are brain damaged but the clarity might motivate
      some fixes and avoid future mistakes.
      Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Vlastimil Babka <vbabka@suse.cz>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Michal Hocko <mhocko@kernel.org>
      Cc: Vitaly Wool <vitalywool@gmail.com>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      dd56b046
    • Mel Gorman's avatar
      mm, page_alloc: only enforce watermarks for order-0 allocations · 97a16fc8
      Mel Gorman authored
      The primary purpose of watermarks is to ensure that reclaim can always
      make forward progress in PF_MEMALLOC context (kswapd and direct reclaim).
      These assume that order-0 allocations are all that is necessary for
      forward progress.
      
      High-order watermarks serve a different purpose.  Kswapd had no high-order
      awareness before they were introduced
      (https://lkml.kernel.org/r/413AA7B2.4000907@yahoo.com.au).  This was
      particularly important when there were high-order atomic requests.  The
      watermarks both gave kswapd awareness and made a reserve for those atomic
      requests.
      
      There are two important side-effects of this.  The most important is that
      a non-atomic high-order request can fail even though free pages are
      available and the order-0 watermarks are ok.  The second is that
      high-order watermark checks are expensive as the free list counts up to
      the requested order must be examined.
      
      With the introduction of MIGRATE_HIGHATOMIC it is no longer necessary to
      have high-order watermarks.  Kswapd and compaction still need high-order
      awareness which is handled by checking that at least one suitable
      high-order page is free.
      
      With the patch applied, there was little difference in the allocation
      failure rates as the atomic reserves are small relative to the number of
      allocation attempts.  The expected impact is that there will never be an
      allocation failure report that shows suitable pages on the free lists.
      
      The one potential side-effect of this is that in a vanilla kernel, the
      watermark checks may have kept a free page for an atomic allocation.  Now,
      we are 100% relying on the HighAtomic reserves and an early allocation to
      have allocated them.  If the first high-order atomic allocation is after
      the system is already heavily fragmented then it'll fail.
      
      [akpm@linux-foundation.org: simplify __zone_watermark_ok(), per Vlastimil]
      Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Vitaly Wool <vitalywool@gmail.com>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      97a16fc8
    • Mel Gorman's avatar
      mm, page_alloc: reserve pageblocks for high-order atomic allocations on demand · 0aaa29a5
      Mel Gorman authored
      High-order watermark checking exists for two reasons -- kswapd high-order
      awareness and protection for high-order atomic requests.  Historically the
      kernel depended on MIGRATE_RESERVE to preserve min_free_kbytes as
      high-order free pages for as long as possible.  This patch introduces
      MIGRATE_HIGHATOMIC that reserves pageblocks for high-order atomic
      allocations on demand and avoids using those blocks for order-0
      allocations.  This is more flexible and reliable than MIGRATE_RESERVE was.
      
      A MIGRATE_HIGHORDER pageblock is created when an atomic high-order
      allocation request steals a pageblock but limits the total number to 1% of
      the zone.  Callers that speculatively abuse atomic allocations for
      long-lived high-order allocations to access the reserve will quickly fail.
       Note that SLUB is currently not such an abuser as it reclaims at least
      once.  It is possible that the pageblock stolen has few suitable
      high-order pages and will need to steal again in the near future but there
      would need to be strong justification to search all pageblocks for an
      ideal candidate.
      
      The pageblocks are unreserved if an allocation fails after a direct
      reclaim attempt.
      
      The watermark checks account for the reserved pageblocks when the
      allocation request is not a high-order atomic allocation.
      
      The reserved pageblocks can not be used for order-0 allocations.  This may
      allow temporary wastage until a failed reclaim reassigns the pageblock.
      This is deliberate as the intent of the reservation is to satisfy a
      limited number of atomic high-order short-lived requests if the system
      requires them.
      
      The stutter benchmark was used to evaluate this but while it was running
      there was a systemtap script that randomly allocated between 1 high-order
      page and 12.5% of memory's worth of order-3 pages using GFP_ATOMIC.  This
      is much larger than the potential reserve and it does not attempt to be
      realistic.  It is intended to stress random high-order allocations from an
      unknown source, show that there is a reduction in failures without
      introducing an anomaly where atomic allocations are more reliable than
      regular allocations.  The amount of memory reserved varied throughout the
      workload as reserves were created and reclaimed under memory pressure.
      The allocation failures once the workload warmed up were as follows;
      
      4.2-rc5-vanilla		70%
      4.2-rc5-atomic-reserve	56%
      
      The failure rate was also measured while building multiple kernels.  The
      failure rate was 14% but is 6% with this patch applied.
      
      Overall, this is a small reduction but the reserves are small relative to
      the number of allocation requests.  In early versions of the patch, the
      failure rate reduced by a much larger amount but that required much larger
      reserves and perversely made atomic allocations seem more reliable than
      regular allocations.
      
      [yalin.wang2010@gmail.com: fix redundant check and a memory leak]
      Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Vitaly Wool <vitalywool@gmail.com>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: default avataryalin wang <yalin.wang2010@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0aaa29a5
    • Mel Gorman's avatar
      mm, page_alloc: remove MIGRATE_RESERVE · 974a786e
      Mel Gorman authored
      MIGRATE_RESERVE preserves an old property of the buddy allocator that
      existed prior to fragmentation avoidance -- min_free_kbytes worth of pages
      tended to remain contiguous until the only alternative was to fail the
      allocation.  At the time it was discovered that high-order atomic
      allocations relied on this property so MIGRATE_RESERVE was introduced.  A
      later patch will introduce an alternative MIGRATE_HIGHATOMIC so this patch
      deletes MIGRATE_RESERVE and supporting code so it'll be easier to review.
      Note that this patch in isolation may look like a false regression if
      someone was bisecting high-order atomic allocation failures.
      Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@suse.com>
      Cc: Vitaly Wool <vitalywool@gmail.com>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      974a786e
    • Mel Gorman's avatar
      mm, page_alloc: delete the zonelist_cache · f77cf4e4
      Mel Gorman authored
      The zonelist cache (zlc) was introduced to skip over zones that were
      recently known to be full.  This avoided expensive operations such as the
      cpuset checks, watermark calculations and zone_reclaim.  The situation
      today is different and the complexity of zlc is harder to justify.
      
      1) The cpuset checks are no-ops unless a cpuset is active and in general
         are a lot cheaper.
      
      2) zone_reclaim is now disabled by default and I suspect that was a large
         source of the cost that zlc wanted to avoid. When it is enabled, it's
         known to be a major source of stalling when nodes fill up and it's
         unwise to hit every other user with the overhead.
      
      3) Watermark checks are expensive to calculate for high-order
         allocation requests. Later patches in this series will reduce the cost
         of the watermark checking.
      
      4) The most important issue is that in the current implementation it
         is possible for a failed THP allocation to mark a zone full for order-0
         allocations and cause a fallback to remote nodes.
      
      The last issue could be addressed with additional complexity but as the
      benefit of zlc is questionable, it is better to remove it.  If stalls due
      to zone_reclaim are ever reported then an alternative would be to
      introduce deferring logic based on a timeout inside zone_reclaim itself
      and leave the page allocator fast paths alone.
      
      The impact on page-allocator microbenchmarks is negligible as they don't
      hit the paths where the zlc comes into play.  Most page-reclaim related
      workloads showed no noticeable difference as a result of the removal.
      
      The impact was noticeable in a workload called "stutter".  One part uses a
      lot of anonymous memory, a second measures mmap latency and a third copies
      a large file.  In an ideal world the latency application would not notice
      the mmap latency.  On a 2-node machine the results of this patch are
      
      stutter
                                   4.3.0-rc1             4.3.0-rc1
                                    baseline              nozlc-v4
      Min         mmap     20.9243 (  0.00%)     20.7716 (  0.73%)
      1st-qrtle   mmap     22.0612 (  0.00%)     22.0680 ( -0.03%)
      2nd-qrtle   mmap     22.3291 (  0.00%)     22.3809 ( -0.23%)
      3rd-qrtle   mmap     25.2244 (  0.00%)     25.2396 ( -0.06%)
      Max-90%     mmap     48.0995 (  0.00%)     28.3713 ( 41.02%)
      Max-93%     mmap     52.5557 (  0.00%)     36.0170 ( 31.47%)
      Max-95%     mmap     55.8173 (  0.00%)     47.3163 ( 15.23%)
      Max-99%     mmap     67.3781 (  0.00%)     70.1140 ( -4.06%)
      Max         mmap  24447.6375 (  0.00%)  12915.1356 ( 47.17%)
      Mean        mmap     33.7883 (  0.00%)     27.7944 ( 17.74%)
      Best99%Mean mmap     27.7825 (  0.00%)     25.2767 (  9.02%)
      Best95%Mean mmap     26.3912 (  0.00%)     23.7994 (  9.82%)
      Best90%Mean mmap     24.9886 (  0.00%)     23.2251 (  7.06%)
      Best50%Mean mmap     22.0157 (  0.00%)     22.0261 ( -0.05%)
      Best10%Mean mmap     21.6705 (  0.00%)     21.6083 (  0.29%)
      Best5%Mean  mmap     21.5581 (  0.00%)     21.4611 (  0.45%)
      Best1%Mean  mmap     21.3079 (  0.00%)     21.1631 (  0.68%)
      
      Note that the maximum stall latency went from 24 seconds to 12 which is
      still bad but an improvement.  The milage varies considerably 2-node
      machine on an earlier test went from 494 seconds to 47 seconds and a
      4-node machine that tested an earlier version of this patch went from a
      worst case stall time of 6 seconds to 67ms.  The nature of the benchmark
      is inherently unpredictable as it is hammering the system and the milage
      will vary between machines.
      
      There is a secondary impact with potentially more direct reclaim because
      zones are now being considered instead of being skipped by zlc.  In this
      particular test run it did not occur so will not be described.  However,
      in at least one test the following was observed
      
      1. Direct reclaim rates were higher. This was likely due to direct reclaim
        being entered instead of the zlc disabling a zone and busy looping.
        Busy looping may have the effect of allowing kswapd to make more
        progress and in some cases may be better overall. If this is found then
        the correct action is to put direct reclaimers to sleep on a waitqueue
        and allow kswapd make forward progress. Busy looping on the zlc is even
        worse than when the allocator used to blindly call congestion_wait().
      
      2. There was higher swap activity as direct reclaim was active.
      
      3. Direct reclaim efficiency was lower. This is related to 1 as more
        scanning activity also encountered more pages that could not be
        immediately reclaimed
      
      In that case, the direct page scan and reclaim rates are noticeable but
      it is not considered a problem for a few reasons
      
      1. The test is primarily concerned with latency. The mmap attempts are also
         faulted which means there are THP allocation requests. The ZLC could
         cause zones to be disabled causing the process to busy loop instead
         of reclaiming.  This looks like elevated direct reclaim activity but
         it's the correct action to take based on what processes requested.
      
      2. The test hammers reclaim and compaction heavily. The number of successful
         THP faults is highly variable but affects the reclaim stats. It's not a
         realistic or reasonable measure of page reclaim activity.
      
      3. No other page-reclaim intensive workload that was tested showed a problem.
      
      4. If a workload is identified that benefitted from the busy looping then it
         should be fixed by having direct reclaimers sleep on a wait queue until
         woken by kswapd instead of busy looping. We had this class of problem before
         when congestion_waits() with a fixed timeout was a brain damaged decision
         but happened to benefit some workloads.
      
      If a workload is identified that relied on the zlc to busy loop then it
      should be fixed correctly and have a direct reclaimer sleep on a waitqueue
      until woken by kswapd.
      Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
      Acked-by: default avatarDavid Rientjes <rientjes@google.com>
      Acked-by: default avatarChristoph Lameter <cl@linux.com>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Cc: Vitaly Wool <vitalywool@gmail.com>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      f77cf4e4
    • Mel Gorman's avatar
      mm, page_alloc: rename __GFP_WAIT to __GFP_RECLAIM · 71baba4b
      Mel Gorman authored
      __GFP_WAIT was used to signal that the caller was in atomic context and
      could not sleep.  Now it is possible to distinguish between true atomic
      context and callers that are not willing to sleep.  The latter should
      clear __GFP_DIRECT_RECLAIM so kswapd will still wake.  As clearing
      __GFP_WAIT behaves differently, there is a risk that people will clear the
      wrong flags.  This patch renames __GFP_WAIT to __GFP_RECLAIM to clearly
      indicate what it does -- setting it allows all reclaim activity, clearing
      them prevents it.
      
      [akpm@linux-foundation.org: fix build]
      [akpm@linux-foundation.org: coding-style fixes]
      Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Cc: Christoph Lameter <cl@linux.com>
      Acked-by: default avatarDavid Rientjes <rientjes@google.com>
      Cc: Vitaly Wool <vitalywool@gmail.com>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      71baba4b
    • Mel Gorman's avatar
      mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep... · d0164adc
      Mel Gorman authored
      mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd
      
      __GFP_WAIT has been used to identify atomic context in callers that hold
      spinlocks or are in interrupts.  They are expected to be high priority and
      have access one of two watermarks lower than "min" which can be referred
      to as the "atomic reserve".  __GFP_HIGH users get access to the first
      lower watermark and can be called the "high priority reserve".
      
      Over time, callers had a requirement to not block when fallback options
      were available.  Some have abused __GFP_WAIT leading to a situation where
      an optimisitic allocation with a fallback option can access atomic
      reserves.
      
      This patch uses __GFP_ATOMIC to identify callers that are truely atomic,
      cannot sleep and have no alternative.  High priority users continue to use
      __GFP_HIGH.  __GFP_DIRECT_RECLAIM identifies callers that can sleep and
      are willing to enter direct reclaim.  __GFP_KSWAPD_RECLAIM to identify
      callers that want to wake kswapd for background reclaim.  __GFP_WAIT is
      redefined as a caller that is willing to enter direct reclaim and wake
      kswapd for background reclaim.
      
      This patch then converts a number of sites
      
      o __GFP_ATOMIC is used by callers that are high priority and have memory
        pools for those requests. GFP_ATOMIC uses this flag.
      
      o Callers that have a limited mempool to guarantee forward progress clear
        __GFP_DIRECT_RECLAIM but keep __GFP_KSWAPD_RECLAIM. bio allocations fall
        into this category where kswapd will still be woken but atomic reserves
        are not used as there is a one-entry mempool to guarantee progress.
      
      o Callers that are checking if they are non-blocking should use the
        helper gfpflags_allow_blocking() where possible. This is because
        checking for __GFP_WAIT as was done historically now can trigger false
        positives. Some exceptions like dm-crypt.c exist where the code intent
        is clearer if __GFP_DIRECT_RECLAIM is used instead of the helper due to
        flag manipulations.
      
      o Callers that built their own GFP flags instead of starting with GFP_KERNEL
        and friends now also need to specify __GFP_KSWAPD_RECLAIM.
      
      The first key hazard to watch out for is callers that removed __GFP_WAIT
      and was depending on access to atomic reserves for inconspicuous reasons.
      In some cases it may be appropriate for them to use __GFP_HIGH.
      
      The second key hazard is callers that assembled their own combination of
      GFP flags instead of starting with something like GFP_KERNEL.  They may
      now wish to specify __GFP_KSWAPD_RECLAIM.  It's almost certainly harmless
      if it's missed in most cases as other activity will wake kswapd.
      Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Vitaly Wool <vitalywool@gmail.com>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d0164adc
    • Mel Gorman's avatar
      mm, page_alloc: remove unnecessary recalculations for dirty zone balancing · c9ab0c4f
      Mel Gorman authored
      File-backed pages that will be immediately written are balanced between
      zones.  This heuristic tries to avoid having a single zone filled with
      recently dirtied pages but the checks are unnecessarily expensive.  Move
      consider_zone_balanced into the alloc_context instead of checking bitmaps
      multiple times.  The patch also gives the parameter a more meaningful
      name.
      Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
      Acked-by: default avatarDavid Rientjes <rientjes@google.com>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Vitaly Wool <vitalywool@gmail.com>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      c9ab0c4f
    • Mel Gorman's avatar
      mm, page_alloc: remove unnecessary parameter from zone_watermark_ok_safe · e2b19197
      Mel Gorman authored
      Overall, the intent of this series is to remove the zonelist cache which
      was introduced to avoid high overhead in the page allocator.  Once this is
      done, it is necessary to reduce the cost of watermark checks.
      
      The series starts with minor micro-optimisations.
      
      Next it notes that GFP flags that affect watermark checks are abused.
      __GFP_WAIT historically identified callers that could not sleep and could
      access reserves.  This was later abused to identify callers that simply
      prefer to avoid sleeping and have other options.  A patch distinguishes
      between atomic callers, high-priority callers and those that simply wish
      to avoid sleep.
      
      The zonelist cache has been around for a long time but it is of dubious
      merit with a lot of complexity and some issues that are explained.  The
      most important issue is that a failed THP allocation can cause a zone to
      be treated as "full".  This potentially causes unnecessary stalls, reclaim
      activity or remote fallbacks.  The issues could be fixed but it's not
      worth it.  The series places a small number of other micro-optimisations
      on top before examining GFP flags watermarks.
      
      High-order watermarks enforcement can cause high-order allocations to fail
      even though pages are free.  The watermark checks both protect high-order
      atomic allocations and make kswapd aware of high-order pages but there is
      a much better way that can be handled using migrate types.  This series
      uses page grouping by mobility to reserve pageblocks for high-order
      allocations with the size of the reservation depending on demand.  kswapd
      awareness is maintained by examining the free lists.  By patch 12 in this
      series, there are no high-order watermark checks while preserving the
      properties that motivated the introduction of the watermark checks.
      
      This patch (of 10):
      
      No user of zone_watermark_ok_safe() specifies alloc_flags.  This patch
      removes the unnecessary parameter.
      Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
      Acked-by: default avatarDavid Rientjes <rientjes@google.com>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Reviewed-by: default avatarChristoph Lameter <cl@linux.com>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      e2b19197
    • Yaowei Bai's avatar
      mm/oom_kill.c: introduce is_sysrq_oom helper · db2a0dd7
      Yaowei Bai authored
      Introduce is_sysrq_oom helper function indicating oom kill triggered
      by sysrq to improve readability.
      
      No functional changes.
      Signed-off-by: default avatarYaowei Bai <bywxiaobai@163.com>
      Acked-by: default avatarDavid Rientjes <rientjes@google.com>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      db2a0dd7
  3. 05 Nov, 2015 10 commits
    • Eric B Munson's avatar
      mm: mlock: add mlock flags to enable VM_LOCKONFAULT usage · b0f205c2
      Eric B Munson authored
      The previous patch introduced a flag that specified pages in a VMA should
      be placed on the unevictable LRU, but they should not be made present when
      the area is created.  This patch adds the ability to set this state via
      the new mlock system calls.
      
      We add MLOCK_ONFAULT for mlock2 and MCL_ONFAULT for mlockall.
      MLOCK_ONFAULT will set the VM_LOCKONFAULT modifier for VM_LOCKED.
      MCL_ONFAULT should be used as a modifier to the two other mlockall flags.
      When used with MCL_CURRENT, all current mappings will be marked with
      VM_LOCKED | VM_LOCKONFAULT.  When used with MCL_FUTURE, the mm->def_flags
      will be marked with VM_LOCKED | VM_LOCKONFAULT.  When used with both
      MCL_CURRENT and MCL_FUTURE, all current mappings and mm->def_flags will be
      marked with VM_LOCKED | VM_LOCKONFAULT.
      
      Prior to this patch, mlockall() will unconditionally clear the
      mm->def_flags any time it is called without MCL_FUTURE.  This behavior is
      maintained after adding MCL_ONFAULT.  If a call to mlockall(MCL_FUTURE) is
      followed by mlockall(MCL_CURRENT), the mm->def_flags will be cleared and
      new VMAs will be unlocked.  This remains true with or without MCL_ONFAULT
      in either mlockall() invocation.
      
      munlock() will unconditionally clear both vma flags.  munlockall()
      unconditionally clears for VMA flags on all VMAs and in the mm->def_flags
      field.
      Signed-off-by: default avatarEric B Munson <emunson@akamai.com>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Cc: Jonathan Corbet <corbet@lwn.net>
      Cc: Catalin Marinas <catalin.marinas@arm.com>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Guenter Roeck <linux@roeck-us.net>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Cc: Michael Kerrisk <mtk.manpages@gmail.com>
      Cc: Ralf Baechle <ralf@linux-mips.org>
      Cc: Shuah Khan <shuahkh@osg.samsung.com>
      Cc: Stephen Rothwell <sfr@canb.auug.org.au>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      b0f205c2
    • Eric B Munson's avatar
      mm: introduce VM_LOCKONFAULT · de60f5f1
      Eric B Munson authored
      The cost of faulting in all memory to be locked can be very high when
      working with large mappings.  If only portions of the mapping will be used
      this can incur a high penalty for locking.
      
      For the example of a large file, this is the usage pattern for a large
      statical language model (probably applies to other statical or graphical
      models as well).  For the security example, any application transacting in
      data that cannot be swapped out (credit card data, medical records, etc).
      
      This patch introduces the ability to request that pages are not
      pre-faulted, but are placed on the unevictable LRU when they are finally
      faulted in.  The VM_LOCKONFAULT flag will be used together with VM_LOCKED
      and has no effect when set without VM_LOCKED.  Setting the VM_LOCKONFAULT
      flag for a VMA will cause pages faulted into that VMA to be added to the
      unevictable LRU when they are faulted or if they are already present, but
      will not cause any missing pages to be faulted in.
      
      Exposing this new lock state means that we cannot overload the meaning of
      the FOLL_POPULATE flag any longer.  Prior to this patch it was used to
      mean that the VMA for a fault was locked.  This means we need the new
      FOLL_MLOCK flag to communicate the locked state of a VMA.  FOLL_POPULATE
      will now only control if the VMA should be populated and in the case of
      VM_LOCKONFAULT, it will not be set.
      Signed-off-by: default avatarEric B Munson <emunson@akamai.com>
      Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Jonathan Corbet <corbet@lwn.net>
      Cc: Catalin Marinas <catalin.marinas@arm.com>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Guenter Roeck <linux@roeck-us.net>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Michael Kerrisk <mtk.manpages@gmail.com>
      Cc: Ralf Baechle <ralf@linux-mips.org>
      Cc: Shuah Khan <shuahkh@osg.samsung.com>
      Cc: Stephen Rothwell <sfr@canb.auug.org.au>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      de60f5f1
    • Eric B Munson's avatar
      mm: mlock: add new mlock system call · a8ca5d0e
      Eric B Munson authored
      With the refactored mlock code, introduce a new system call for mlock.
      The new call will allow the user to specify what lock states are being
      added.  mlock2 is trivial at the moment, but a follow on patch will add a
      new mlock state making it useful.
      Signed-off-by: default avatarEric B Munson <emunson@akamai.com>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Catalin Marinas <catalin.marinas@arm.com>
      Cc: Stephen Rothwell <sfr@canb.auug.org.au>
      Cc: Guenter Roeck <linux@roeck-us.net>
      Cc: Jonathan Corbet <corbet@lwn.net>
      Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Cc: Michael Kerrisk <mtk.manpages@gmail.com>
      Cc: Ralf Baechle <ralf@linux-mips.org>
      Cc: Shuah Khan <shuahkh@osg.samsung.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      a8ca5d0e
    • Eric B Munson's avatar
      mm: mlock: refactor mlock, munlock, and munlockall code · 1aab92ec
      Eric B Munson authored
      mlock() allows a user to control page out of program memory, but this
      comes at the cost of faulting in the entire mapping when it is allocated.
      For large mappings where the entire area is not necessary this is not
      ideal.  Instead of forcing all locked pages to be present when they are
      allocated, this set creates a middle ground.  Pages are marked to be
      placed on the unevictable LRU (locked) when they are first used, but they
      are not faulted in by the mlock call.
      
      This series introduces a new mlock() system call that takes a flags
      argument along with the start address and size.  This flags argument gives
      the caller the ability to request memory be locked in the traditional way,
      or to be locked after the page is faulted in.  A new MCL flag is added to
      mirror the lock on fault behavior from mlock() in mlockall().
      
      There are two main use cases that this set covers.  The first is the
      security focussed mlock case.  A buffer is needed that cannot be written
      to swap.  The maximum size is known, but on average the memory used is
      significantly less than this maximum.  With lock on fault, the buffer is
      guaranteed to never be paged out without consuming the maximum size every
      time such a buffer is created.
      
      The second use case is focussed on performance.  Portions of a large file
      are needed and we want to keep the used portions in memory once accessed.
      This is the case for large graphical models where the path through the
      graph is not known until run time.  The entire graph is unlikely to be
      used in a given invocation, but once a node has been used it needs to stay
      resident for further processing.  Given these constraints we have a number
      of options.  We can potentially waste a large amount of memory by mlocking
      the entire region (this can also cause a significant stall at startup as
      the entire file is read in).  We can mlock every page as we access them
      without tracking if the page is already resident but this introduces large
      overhead for each access.  The third option is mapping the entire region
      with PROT_NONE and using a signal handler for SIGSEGV to
      mprotect(PROT_READ) and mlock() the needed page.  Doing this page at a
      time adds a significant performance penalty.  Batching can be used to
      mitigate this overhead, but in order to safely avoid trying to mprotect
      pages outside of the mapping, the boundaries of each mapping to be used in
      this way must be tracked and available to the signal handler.  This is
      precisely what the mm system in the kernel should already be doing.
      
      For mlock(MLOCK_ONFAULT) the user is charged against RLIMIT_MEMLOCK as if
      mlock(MLOCK_LOCKED) or mmap(MAP_LOCKED) was used, so when the VMA is
      created not when the pages are faulted in.  For mlockall(MCL_ONFAULT) the
      user is charged as if MCL_FUTURE was used.  This decision was made to keep
      the accounting checks out of the page fault path.
      
      To illustrate the benefit of this set I wrote a test program that mmaps a
      5 GB file filled with random data and then makes 15,000,000 accesses to
      random addresses in that mapping.  The test program was run 20 times for
      each setup.  Results are reported for two program portions, setup and
      execution.  The setup phase is calling mmap and optionally mlock on the
      entire region.  For most experiments this is trivial, but it highlights
      the cost of faulting in the entire region.  Results are averages across
      the 20 runs in milliseconds.
      
      mmap with mlock(MLOCK_LOCKED) on entire range:
      Setup avg:      8228.666
      Processing avg: 8274.257
      
      mmap with mlock(MLOCK_LOCKED) before each access:
      Setup avg:      0.113
      Processing avg: 90993.552
      
      mmap with PROT_NONE and signal handler and batch size of 1 page:
      With the default value in max_map_count, this gets ENOMEM as I attempt
      to change the permissions, after upping the sysctl significantly I get:
      Setup avg:      0.058
      Processing avg: 69488.073
      mmap with PROT_NONE and signal handler and batch size of 8 pages:
      Setup avg:      0.068
      Processing avg: 38204.116
      
      mmap with PROT_NONE and signal handler and batch size of 16 pages:
      Setup avg:      0.044
      Processing avg: 29671.180
      
      mmap with mlock(MLOCK_ONFAULT) on entire range:
      Setup avg:      0.189
      Processing avg: 17904.899
      
      The signal handler in the batch cases faulted in memory in two steps to
      avoid having to know the start and end of the faulting mapping.  The first
      step covers the page that caused the fault as we know that it will be
      possible to lock.  The second step speculatively tries to mlock and
      mprotect the batch size - 1 pages that follow.  There may be a clever way
      to avoid this without having the program track each mapping to be covered
      by this handeler in a globally accessible structure, but I could not find
      it.  It should be noted that with a large enough batch size this two step
      fault handler can still cause the program to crash if it reaches far
      beyond the end of the mapping.
      
      These results show that if the developer knows that a majority of the
      mapping will be used, it is better to try and fault it in at once,
      otherwise mlock(MLOCK_ONFAULT) is significantly faster.
      
      The performance cost of these patches are minimal on the two benchmarks I
      have tested (stream and kernbench).  The following are the average values
      across 20 runs of stream and 10 runs of kernbench after a warmup run whose
      results were discarded.
      
      Avg throughput in MB/s from stream using 1000000 element arrays
      Test     4.2-rc1      4.2-rc1+lock-on-fault
      Copy:    10,566.5     10,421
      Scale:   10,685       10,503.5
      Add:     12,044.1     11,814.2
      Triad:   12,064.8     11,846.3
      
      Kernbench optimal load
                       4.2-rc1  4.2-rc1+lock-on-fault
      Elapsed Time     78.453   78.991
      User Time        64.2395  65.2355
      System Time      9.7335   9.7085
      Context Switches 22211.5  22412.1
      Sleeps           14965.3  14956.1
      
      This patch (of 6):
      
      Extending the mlock system call is very difficult because it currently
      does not take a flags argument.  A later patch in this set will extend
      mlock to support a middle ground between pages that are locked and faulted
      in immediately and unlocked pages.  To pave the way for the new system
      call, the code needs some reorganization so that all the actual entry
      point handles is checking input and translating to VMA flags.
      Signed-off-by: default avatarEric B Munson <emunson@akamai.com>
      Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Cc: Michael Kerrisk <mtk.manpages@gmail.com>
      Cc: Catalin Marinas <catalin.marinas@arm.com>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Guenter Roeck <linux@roeck-us.net>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Jonathan Corbet <corbet@lwn.net>
      Cc: Ralf Baechle <ralf@linux-mips.org>
      Cc: Shuah Khan <shuahkh@osg.samsung.com>
      Cc: Stephen Rothwell <sfr@canb.auug.org.au>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      1aab92ec
    • Andrey Ryabinin's avatar
      kasan: always taint kernel on report · eb06f43f
      Andrey Ryabinin authored
      Currently we already taint the kernel in some cases.  E.g.  if we hit some
      bug in slub memory we call object_err() which will taint the kernel with
      TAINT_BAD_PAGE flag.  But for other kind of bugs kernel left untainted.
      
      Always taint with TAINT_BAD_PAGE if kasan found some bug.  This is useful
      for automated testing.
      Signed-off-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
      Cc: Alexander Potapenko <glider@google.com>
      Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      eb06f43f
    • Andrey Ryabinin's avatar
      mm, slub, kasan: enable user tracking by default with KASAN=y · 89d3c87e
      Andrey Ryabinin authored
      It's recommended to have slub's user tracking enabled with CONFIG_KASAN,
      because:
      
      a) User tracking disables slab merging which improves
          detecting out-of-bounds accesses.
      b) User tracking metadata acts as redzone which also improves
          detecting out-of-bounds accesses.
      c) User tracking provides additional information about object.
          This information helps to understand bugs.
      
      Currently it is not enabled by default.  Besides recompiling the kernel
      with KASAN and reinstalling it, user also have to change the boot cmdline,
      which is not very handy.
      
      Enable slub user tracking by default with KASAN=y, since there is no good
      reason to not do this.
      
      [akpm@linux-foundation.org: little fixes, per David]
      Signed-off-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      89d3c87e
    • Xishi Qiu's avatar
      kasan: use IS_ALIGNED in memory_is_poisoned_8() · 10f70262
      Xishi Qiu authored
      Use IS_ALIGNED() to determine whether the shadow span two bytes.  It
      generates less code and more readable.  Also add some comments in shadow
      check functions.
      Signed-off-by: default avatarXishi Qiu <qiuxishi@huawei.com>
      Acked-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
      Cc: Andrey Konovalov <adech.fo@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      10f70262
    • Wang Long's avatar
      kasan: Fix a type conversion error · e0d57714
      Wang Long authored
      The current KASAN code can not find the following out-of-bounds bugs:
      
              char *ptr;
              ptr = kmalloc(8, GFP_KERNEL);
              memset(ptr+7, 0, 2);
      
      the cause of the problem is the type conversion error in
      *memory_is_poisoned_n* function.  So this patch fix that.
      Signed-off-by: default avatarWang Long <long.wanglong@huawei.com>
      Acked-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
      Cc: Vladimir Murzin <vladimir.murzin@arm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      e0d57714
    • Andrey Konovalov's avatar
      kasan: update reference to kasan prototype repo · 5d0926ef
      Andrey Konovalov authored
      Update the reference to the kasan prototype repository on github, since it
      was renamed.
      Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
      Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
      Cc: Dmitry Vyukov <dvyukov@google.com>
      Cc: Alexander Potapenko <glider@google.com>
      Cc: Konstantin Serebryany <kcc@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      5d0926ef
    • Andrey Konovalov's avatar
      kasan: update log messages · 25add7ec
      Andrey Konovalov authored
      We decided to use KASAN as the short name of the tool and
      KernelAddressSanitizer as the full one.  Update log messages according to
      that.
      Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
      Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
      Cc: Dmitry Vyukov <dvyukov@google.com>
      Cc: Alexander Potapenko <glider@google.com>
      Cc: Konstantin Serebryany <kcc@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      25add7ec