1. 14 Jul, 2008 1 commit
  2. 28 Apr, 2008 1 commit
    • Christoph Lameter's avatar
      PAGEFLAGS_EXTENDED and separate page flags for Head and Tail · e20b8cca
      Christoph Lameter authored
      
      
      Having separate page flags for the head and the tail of a compound page allows
      the compiler to use bitops instead of operations on a word to check for a tail
      page.  That is f.e.  important for virt_to_head_page() which is used in
      various critical code paths (kfree for example):
      
      Code for PageTail(page)
      
      Before:
      
       mov    (%rdi),%rdx		page->flags
       mov    %rdx,%rax		3 bytes
       and    $0x12000,%eax		5 bytes
       cmp    $0x12000,%rax		6 bytes
       je     897 <kfree+0xa7>
      
      After:
      
       mov    (%rdi),%rax
       test   $0x40,%ah			(3 bytes)
       jne    887 <kfree+0x97>
      
      So we go from 14 bytes to 3 bytes and from 3 instructions to one.  From the
      use of 2 registers we go to none.
      
      We can only use page flags for this if we have page flags available.  This
      patch introduces CONFIG_PAGEFLAGS_EXTENDED that is set if pageflags are not
      scarce due to SPARSEMEM using page flags for its sectionid on 32 bit NUMA
      platforms.
      
      Additional page flag definitions can be added to the CONFIG_PAGEFLAGS_EXTENDED
      section in page-flags.h if the functionality depends on PAGEFLAGS_EXTENDED or
      if more page flag overlapping tricks are used for the !PAGEFLAGS_EXTENDED
      fallback (the upcoming virtual compound patch may hook in here and Rik's/Lee's
      additional page flags to solve the reclaim issues could also be added there
      [hint...  hint...  where are these patchsets?]).
      
      Avoiding the overlaying of Pg_reclaim also clears the way for possible use of
      compound pages for the pagecache or on the LRU.
      Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
      Cc: Nick Piggin <nickpiggin@yahoo.com.au>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      e20b8cca
  3. 27 Jan, 2008 1 commit
  4. 17 Dec, 2007 1 commit
  5. 19 Oct, 2007 1 commit
  6. 16 Oct, 2007 3 commits
    • Jeremy Fitzhardinge's avatar
      xen: lock pte pages while pinning/unpinning · 74260714
      Jeremy Fitzhardinge authored
      
      
      When a pagetable is created, it is made globally visible in the rmap
      prio tree before it is pinned via arch_dup_mmap(), and remains in the
      rmap tree while it is unpinned with arch_exit_mmap().
      
      This means that other CPUs may race with the pinning/unpinning
      process, and see a pte between when it gets marked RO and actually
      pinned, causing any pte updates to fail with write-protect faults.
      
      As a result, all pte pages must be properly locked, and only unlocked
      once the pinning/unpinning process has finished.
      
      In order to avoid taking spinlocks for the whole pagetable - which may
      overflow the PREEMPT_BITS portion of preempt counter - it locks and pins
      each pte page individually, and then finally pins the whole pagetable.
      Signed-off-by: default avatarJeremy Fitzhardinge <jeremy@xensource.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Hugh Dickens <hugh@veritas.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andi Kleen <ak@suse.de>
      Cc: Keir Fraser <keir@xensource.com>
      Cc: Jan Beulich <jbeulich@novell.com>
      74260714
    • KAMEZAWA Hiroyuki's avatar
      memory unplug: page offline · 0c0e6195
      KAMEZAWA Hiroyuki authored
      
      
      Logic.
       - set all pages in  [start,end)  as isolated migration-type.
         by this, all free pages in the range will be not-for-use.
       - Migrate all LRU pages in the range.
       - Test all pages in the range's refcnt is zero or not.
      
      Todo:
       - allocate migration destination page from better area.
       - confirm page_count(page)== 0 && PageReserved(page) page is safe to be freed..
       (I don't like this kind of page but..
       - Find out pages which cannot be migrated.
       - more running tests.
       - Use reclaim for unplugging other memory type area.
      Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Signed-off-by: default avatarYasunori Goto <y-goto@jp.fujitsu.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0c0e6195
    • Andy Whitcroft's avatar
      vmemmap: generify initialisation via helpers · 29c71111
      Andy Whitcroft authored
      
      
      Convert the common vmemmap population into initialisation helpers for use by
      architecture vmemmap populators.  All architecture implementing the
      SPARSEMEM_VMEMMAP variant supply an architecture specific vmemmap_populate()
      initialiser, which may make use of the helpers.
      
      This allows us to clean up and remove the initialisation Kconfig entries.
      With this patch there is a single SPARSEMEM_VMEMMAP_ENABLE Kconfig option to
      indicate use of that variant.
      Signed-off-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Acked-by: default avatarChristoph Lameter <clameter@sgi.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      29c71111
  7. 06 Oct, 2007 1 commit
    • Jeremy Fitzhardinge's avatar
      xen: disable split pte locks for now · 67dd5a25
      Jeremy Fitzhardinge authored
      
      
      When pinning and unpinning pagetables, we must protect them against
      being used by other CPUs, lest they see the pagetable in an
      intermediate read-only-but-not-pinned state.
      
      When using split pte locks, doing this properly would require taking
      all the pte locks for the pagetable while pinning, but this may overflow
      the PREEMPT_BITS part of the preempt counter if the process has mapped
      more than about 512M of memory.
      
      However, failing to take the pte locks causes write-protect faults when
      the pageout code is trying to clear the Access bit on a pte which is part
      of a freshy created and still being pinned process after fork.
      
      This is a short-term fix until the problem is solved properly.
      Signed-off-by: default avatarJeremy Fitzhardinge <jeremy@xensource.com>
      Acked-by: default avatarRik van Riel <riel@redhat.com>
      Acked-by: default avatarHugh Dickins <hugh@veritas.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andi Kleen <ak@suse.de>
      Cc: Keir Fraser <keir@xensource.com>
      Cc: Jan Beulich <jbeulich@novell.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      67dd5a25
  8. 29 Jul, 2007 1 commit
  9. 17 Jul, 2007 1 commit
  10. 16 Jul, 2007 1 commit
  11. 07 Jun, 2007 1 commit
  12. 13 May, 2007 1 commit
  13. 08 May, 2007 1 commit
  14. 07 May, 2007 1 commit
    • Christoph Lameter's avatar
      Quicklists for page table pages · 6225e937
      Christoph Lameter authored
      
      
      On x86_64 this cuts allocation overhead for page table pages down to a
      fraction (kernel compile / editing load.  TSC based measurement of times spend
      in each function):
      
      no quicklist
      
      pte_alloc               1569048 4.3s(401ns/2.7us/179.7us)
      pmd_alloc                780988 2.1s(337ns/2.7us/86.1us)
      pud_alloc                780072 2.2s(424ns/2.8us/300.6us)
      pgd_alloc                260022 1s(920ns/4us/263.1us)
      
      quicklist:
      
      pte_alloc                452436 573.4ms(8ns/1.3us/121.1us)
      pmd_alloc                196204 174.5ms(7ns/889ns/46.1us)
      pud_alloc                195688 172.4ms(7ns/881ns/151.3us)
      pgd_alloc                 65228 9.8ms(8ns/150ns/6.1us)
      
      pgd allocations are the most complex and there we see the most dramatic
      improvement (may be we can cut down the amount of pgds cached somewhat?).  But
      even the pte allocations still see a doubling of performance.
      
      1. Proven code from the IA64 arch.
      
      	The method used here has been fine tuned for years and
      	is NUMA aware. It is based on the knowledge that accesses
      	to page table pages are sparse in nature. Taking a page
      	off the freelists instead of allocating a zeroed pages
      	allows a reduction of number of cachelines touched
      	in addition to getting rid of the slab overhead. So
      	performance improves. This is particularly useful if pgds
      	contain standard mappings. We can save on the teardown
      	and setup of such a page if we have some on the quicklists.
      	This includes avoiding lists operations that are otherwise
      	necessary on alloc and free to track pgds.
      
      2. Light weight alternative to use slab to manage page size pages
      
      	Slab overhead is significant and even page allocator use
      	is pretty heavy weight. The use of a per cpu quicklist
      	means that we touch only two cachelines for an allocation.
      	There is no need to access the page_struct (unless arch code
      	needs to fiddle around with it). So the fast past just
      	means bringing in one cacheline at the beginning of the
      	page. That same cacheline may then be used to store the
      	page table entry. Or a second cacheline may be used
      	if the page table entry is not in the first cacheline of
      	the page. The current code will zero the page which means
      	touching 32 cachelines (assuming 128 byte). We get down
      	from 32 to 2 cachelines in the fast path.
      
      3. x86_64 gets lightweight page table page management.
      
      	This will allow x86_64 arch code to faster repopulate pgds
      	and other page table entries. The list operations for pgds
      	are reduced in the same way as for i386 to the point where
      	a pgd is allocated from the page allocator and when it is
      	freed back to the page allocator. A pgd can pass through
      	the quicklists without having to be reinitialized.
      
      64 Consolidation of code from multiple arches
      
      	So far arches have their own implementation of quicklist
      	management. This patch moves that feature into the core allowing
      	an easier maintenance and consistent management of quicklists.
      
      Page table pages have the characteristics that they are typically zero or in a
      known state when they are freed.  This is usually the exactly same state as
      needed after allocation.  So it makes sense to build a list of freed page
      table pages and then consume the pages already in use first.  Those pages have
      already been initialized correctly (thus no need to zero them) and are likely
      already cached in such a way that the MMU can use them most effectively.  Page
      table pages are used in a sparse way so zeroing them on allocation is not too
      useful.
      
      Such an implementation already exits for ia64.  Howver, that implementation
      did not support constructors and destructors as needed by i386 / x86_64.  It
      also only supported a single quicklist.  The implementation here has
      constructor and destructor support as well as the ability for an arch to
      specify how many quicklists are needed.
      
      Quicklists are defined by an arch defining CONFIG_QUICKLIST.  If more than one
      quicklist is necessary then we can define NR_QUICK for additional lists.  F.e.
       i386 needs two and thus has
      
      config NR_QUICK
      	int
      	default 2
      
      If an arch has requested quicklist support then pages can be allocated
      from the quicklist (or from the page allocator if the quicklist is
      empty) via:
      
      quicklist_alloc(<quicklist-nr>, <gfpflags>, <constructor>)
      
      Page table pages can be freed using:
      
      quicklist_free(<quicklist-nr>, <destructor>, <page>)
      
      Pages must have a definite state after allocation and before
      they are freed. If no constructor is specified then pages
      will be zeroed on allocation and must be zeroed before they are
      freed.
      
      If a constructor is used then the constructor will establish
      a definite page state. F.e. the i386 and x86_64 pgd constructors
      establish certain mappings.
      
      Constructors and destructors can also be used to track the pages.
      i386 and x86_64 use a list of pgds in order to be able to dynamically
      update standard mappings.
      Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Andi Kleen <ak@suse.de>
      Cc: "Luck, Tony" <tony.luck@intel.com>
      Cc: William Lee Irwin III <wli@holomorphy.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      6225e937
  15. 11 Feb, 2007 3 commits
    • Christoph Lameter's avatar
      [PATCH] Set CONFIG_ZONE_DMA for arches with GENERIC_ISA_DMA · 5ac6da66
      Christoph Lameter authored
      
      
      As Andi pointed out: CONFIG_GENERIC_ISA_DMA only disables the ISA DMA
      channel management.  Other functionality may still expect GFP_DMA to
      provide memory below 16M.  So we need to make sure that CONFIG_ZONE_DMA is
      set independent of CONFIG_GENERIC_ISA_DMA.  Undo the modifications to
      mm/Kconfig where we made ZONE_DMA dependent on GENERIC_ISA_DMA and set
      theses explicitly in each arches Kconfig.
      
      Reviews must occur for each arch in order to determine if ZONE_DMA can be
      switched off.  It can only be switched off if we know that all devices
      supported by a platform are capable of performing DMA transfers to all of
      memory (Some arches already support this: uml, avr32, sh sh64, parisc and
      IA64/Altix).
      
      In order to switch ZONE_DMA off conditionally, one would have to establish
      a scheme by which one can assure that no drivers are enabled that are only
      capable of doing I/O to a part of memory, or one needs to provide an
      alternate means of performing an allocation from a specific range of memory
      (like provided by alloc_pages_range()) and insure that all drivers use that
      call.  In that case the arches alloc_dma_coherent() may need to be modified
      to call alloc_pages_range() instead of relying on GFP_DMA.
      Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      5ac6da66
    • Christoph Lameter's avatar
      [PATCH] optional ZONE_DMA: optional ZONE_DMA in the VM · 4b51d669
      Christoph Lameter authored
      
      
      Make ZONE_DMA optional in core code.
      
      - ifdef all code for ZONE_DMA and related definitions following the example
        for ZONE_DMA32 and ZONE_HIGHMEM.
      
      - Without ZONE_DMA, ZONE_HIGHMEM and ZONE_DMA32 we get to a ZONES_SHIFT of
        0.
      
      - Modify the VM statistics to work correctly without a DMA zone.
      
      - Modify slab to not create DMA slabs if there is no ZONE_DMA.
      
      [akpm@osdl.org: cleanup]
      [jdike@addtoit.com: build fix]
      [apw@shadowen.org: Simplify calculation of the number of bits we need for ZONES_SHIFT]
      Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
      Cc: Andi Kleen <ak@suse.de>
      Cc: "Luck, Tony" <tony.luck@intel.com>
      Cc: Kyle McMartin <kyle@mcmartin.ca>
      Cc: Matthew Wilcox <willy@debian.org>
      Cc: James Bottomley <James.Bottomley@steeleye.com>
      Cc: Paul Mundt <lethal@linux-sh.org>
      Signed-off-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Signed-off-by: default avatarJeff Dike <jdike@addtoit.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      4b51d669
    • Christoph Lameter's avatar
      [PATCH] optional ZONE_DMA: introduce CONFIG_ZONE_DMA · 66701b14
      Christoph Lameter authored
      
      
      This patch simply defines CONFIG_ZONE_DMA for all arches.  We later do special
      things with CONFIG_ZONE_DMA after the VM and an arch are prepared to work
      without ZONE_DMA.
      
      CONFIG_ZONE_DMA can be defined in two ways depending on how an architecture
      handles ISA DMA.
      
      First if CONFIG_GENERIC_ISA_DMA is set by the arch then we know that the arch
      needs ZONE_DMA because ISA DMA devices are supported.  We can catch this in
      mm/Kconfig and do not need to modify arch code.
      
      Second, arches may use ZONE_DMA in an unknown way.  We set CONFIG_ZONE_DMA for
      all arches that do not set CONFIG_GENERIC_ISA_DMA in order to insure backwards
      compatibility.  The arches may later undefine ZONE_DMA if their arch code has
      been verified to not depend on ZONE_DMA.
      Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
      Cc: Andi Kleen <ak@suse.de>
      Cc: "Luck, Tony" <tony.luck@intel.com>
      Cc: Kyle McMartin <kyle@mcmartin.ca>
      Cc: Matthew Wilcox <willy@debian.org>
      Cc: James Bottomley <James.Bottomley@steeleye.com>
      Cc: Paul Mundt <lethal@linux-sh.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      66701b14
  16. 03 Oct, 2006 2 commits
  17. 01 Oct, 2006 1 commit
  18. 29 Jun, 2006 1 commit
  19. 27 Jun, 2006 2 commits
  20. 23 Jun, 2006 1 commit
  21. 25 Mar, 2006 1 commit
  22. 22 Mar, 2006 1 commit
    • Christoph Lameter's avatar
      [PATCH] page migration reorg · b20a3503
      Christoph Lameter authored
      
      
      Centralize the page migration functions in anticipation of additional
      tinkering.  Creates a new file mm/migrate.c
      
      1. Extract buffer_migrate_page() from fs/buffer.c
      
      2. Extract central migration code from vmscan.c
      
      3. Extract some components from mempolicy.c
      
      4. Export pageout() and remove_from_swap() from vmscan.c
      
      5. Make it possible to configure NUMA systems without page migration
         and non-NUMA systems with page migration.
      
      I had to so some #ifdeffing in mempolicy.c that may need a cleanup.
      Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      b20a3503
  23. 08 Jan, 2006 1 commit
  24. 06 Jan, 2006 1 commit
  25. 23 Nov, 2005 1 commit
    • Hugh Dickins's avatar
      [PATCH] mm: update split ptlock Kconfig · 7b6ac9df
      Hugh Dickins authored
      
      
      Closer attention to the arithmetic shows that neither ppc64 nor sparc really
      uses one page for multiple page tables: how on earth could they, while
      pte_alloc_one returns just a struct page pointer, with no offset?
      
      Well, arm26 manages it by returning a pte_t pointer cast to a struct page
      pointer, harumph, then compensating in its pmd_populate.  But arm26 is never
      SMP, so it's not a problem for split ptlock either.
      
      And the PA-RISC situation has been recently improved: CONFIG_PA20 works
      without the 16-byte alignment which inflated its spinlock_t.  But the current
      union of spinlock_t with private does make the 7xxx struct page significantly
      larger, even without debug, so disable its split ptlock.
      Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      7b6ac9df
  26. 07 Nov, 2005 1 commit
  27. 29 Oct, 2005 2 commits
    • Dave Hansen's avatar
      [PATCH] memory hotplug: sysfs and add/remove functions · 3947be19
      Dave Hansen authored
      
      
      This adds generic memory add/remove and supporting functions for memory
      hotplug into a new file as well as a memory hotplug kernel config option.
      
      Individual architecture patches will follow.
      
      For now, disable memory hotplug when swsusp is enabled.  There's a lot of
      churn there right now.  We'll fix it up properly once it calms down.
      Signed-off-by: default avatarMatt Tolentino <matthew.e.tolentino@intel.com>
      Signed-off-by: default avatarDave Hansen <haveblue@us.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      3947be19
    • Hugh Dickins's avatar
      [PATCH] mm: split page table lock · 4c21e2f2
      Hugh Dickins authored
      
      
      Christoph Lameter demonstrated very poor scalability on the SGI 512-way, with
      a many-threaded application which concurrently initializes different parts of
      a large anonymous area.
      
      This patch corrects that, by using a separate spinlock per page table page, to
      guard the page table entries in that page, instead of using the mm's single
      page_table_lock.  (But even then, page_table_lock is still used to guard page
      table allocation, and anon_vma allocation.)
      
      In this implementation, the spinlock is tucked inside the struct page of the
      page table page: with a BUILD_BUG_ON in case it overflows - which it would in
      the case of 32-bit PA-RISC with spinlock debugging enabled.
      
      Splitting the lock is not quite for free: another cacheline access.  Ideally,
      I suppose we would use split ptlock only for multi-threaded processes on
      multi-cpu machines; but deciding that dynamically would have its own costs.
      So for now enable it by config, at some number of cpus - since the Kconfig
      language doesn't support inequalities, let preprocessor compare that with
      NR_CPUS.  But I don't think it's worth being user-configurable: for good
      testing of both split and unsplit configs, split now at 4 cpus, and perhaps
      change that to 8 later.
      
      There is a benefit even for singly threaded processes: kswapd can be attacking
      one part of the mm while another part is busy faulting.
      Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      4c21e2f2
  28. 17 Sep, 2005 1 commit
  29. 05 Sep, 2005 2 commits
    • Bob Picco's avatar
      [PATCH] sparsemem extreme implementation · 3e347261
      Bob Picco authored
      
      
      With cleanups from Dave Hansen <haveblue@us.ibm.com>
      
      SPARSEMEM_EXTREME makes mem_section a one dimensional array of pointers to
      mem_sections.  This two level layout scheme is able to achieve smaller
      memory requirements for SPARSEMEM with the tradeoff of an additional shift
      and load when fetching the memory section.  The current SPARSEMEM
      implementation is a one dimensional array of mem_sections which is the
      default SPARSEMEM configuration.  The patch attempts isolates the
      implementation details of the physical layout of the sparsemem section
      array.
      
      SPARSEMEM_EXTREME requires bootmem to be functioning at the time of
      memory_present() calls.  This is not always feasible, so architectures
      which do not need it may allocate everything statically by using
      SPARSEMEM_STATIC.
      Signed-off-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Signed-off-by: default avatarBob Picco <bob.picco@hp.com>
      Signed-off-by: default avatarDave Hansen <haveblue@us.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      3e347261
    • Bob Picco's avatar
      [PATCH] SPARSEMEM EXTREME · 802f192e
      Bob Picco authored
      
      
      A new option for SPARSEMEM is ARCH_SPARSEMEM_EXTREME.  Architecture
      platforms with a very sparse physical address space would likely want to
      select this option.  For those architecture platforms that don't select the
      option, the code generated is equivalent to SPARSEMEM currently in -mm.
      I'll be posting a patch on ia64 ml which uses this new SPARSEMEM feature.
      
      ARCH_SPARSEMEM_EXTREME makes mem_section a one dimensional array of
      pointers to mem_sections.  This two level layout scheme is able to achieve
      smaller memory requirements for SPARSEMEM with the tradeoff of an
      additional shift and load when fetching the memory section.  The current
      SPARSEMEM -mm implementation is a one dimensional array of mem_sections
      which is the default SPARSEMEM configuration.  The patch attempts isolates
      the implementation details of the physical layout of the sparsemem section
      array.
      
      ARCH_SPARSEMEM_EXTREME depends on 64BIT and is by default boolean false.
      
      I've boot tested under aim load ia64 configured for ARCH_SPARSEMEM_EXTREME.
       I've also boot tested a 4 way Opteron machine with !ARCH_SPARSEMEM_EXTREME
      and tested with aim.
      Signed-off-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Signed-off-by: default avatarBob Picco <bob.picco@hp.com>
      Signed-off-by: default avatarDave Hansen <haveblue@us.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      802f192e
  30. 23 Jun, 2005 3 commits
    • Andy Whitcroft's avatar
      [PATCH] sparsemem memory model · d41dee36
      Andy Whitcroft authored
      
      
      Sparsemem abstracts the use of discontiguous mem_maps[].  This kind of
      mem_map[] is needed by discontiguous memory machines (like in the old
      CONFIG_DISCONTIGMEM case) as well as memory hotplug systems.  Sparsemem
      replaces DISCONTIGMEM when enabled, and it is hoped that it can eventually
      become a complete replacement.
      
      A significant advantage over DISCONTIGMEM is that it's completely separated
      from CONFIG_NUMA.  When producing this patch, it became apparent in that NUMA
      and DISCONTIG are often confused.
      
      Another advantage is that sparse doesn't require each NUMA node's ranges to be
      contiguous.  It can handle overlapping ranges between nodes with no problems,
      where DISCONTIGMEM currently throws away that memory.
      
      Sparsemem uses an array to provide different pfn_to_page() translations for
      each SECTION_SIZE area of physical memory.  This is what allows the mem_map[]
      to be chopped up.
      
      In order to do quick pfn_to_page() operations, the section number of the page
      is encoded in page->flags.  Part of the sparsemem infrastructure enables
      sharing of these bits more dynamically (at compile-time) between the
      page_zone() and sparsemem operations.  However, on 32-bit architectures, the
      number of bits is quite limited, and may require growing the size of the
      page->flags type in certain conditions.  Several things might force this to
      occur: a decrease in the SECTION_SIZE (if you want to hotplug smaller areas of
      memory), an increase in the physical address space, or an increase in the
      number of used page->flags.
      
      One thing to note is that, once sparsemem is present, the NUMA node
      information no longer needs to be stored in the page->flags.  It might provide
      speed increases on certain platforms and will be stored there if there is
      room.  But, if out of room, an alternate (theoretically slower) mechanism is
      used.
      
      This patch introduces CONFIG_FLATMEM.  It is used in almost all cases where
      there used to be an #ifndef DISCONTIG, because SPARSEMEM and DISCONTIGMEM
      often have to compile out the same areas of code.
      Signed-off-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Signed-off-by: default avatarDave Hansen <haveblue@us.ibm.com>
      Signed-off-by: default avatarMartin Bligh <mbligh@aracnet.com>
      Signed-off-by: default avatarAdrian Bunk <bunk@stusta.de>
      Signed-off-by: default avatarYasunori Goto <y-goto@jp.fujitsu.com>
      Signed-off-by: default avatarBob Picco <bob.picco@hp.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      d41dee36
    • Andy Whitcroft's avatar
      [PATCH] generify memory present · af705362
      Andy Whitcroft authored
      
      
      Allow architectures to indicate that they will be providing hooks to indice
      installed memory areas, memory_present().  Provide prototypes for the i386
      implementation.
      Signed-off-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Signed-off-by: default avatarDave Hansen <haveblue@us.ibm.com>
      Signed-off-by: default avatarMartin Bligh <mbligh@aracnet.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      af705362
    • Dave Hansen's avatar
      [PATCH] mm/Kconfig: give DISCONTIG more help text · 785dcd44
      Dave Hansen authored
      
      
      This gives DISCONTIGMEM a bit more help text to explain what it does, not just
      when to choose it.
      Signed-off-by: default avatarDave Hansen <haveblue@us.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      785dcd44