1. 23 Jan, 2014 1 commit
  2. 21 Jan, 2014 1 commit
    • Jerome Marchand's avatar
      mm: add overcommit_kbytes sysctl variable · 49f0ce5f
      Jerome Marchand authored
      Some applications that run on HPC clusters are designed around the
      availability of RAM and the overcommit ratio is fine tuned to get the
      maximum usage of memory without swapping.  With growing memory, the
      1%-of-all-RAM grain provided by overcommit_ratio has become too coarse
      for these workload (on a 2TB machine it represents no less than 20GB).
      This patch adds the new overcommit_kbytes sysctl variable that allow a
      much finer grain.
      [akpm@linux-foundation.org: coding-style fixes]
      [akpm@linux-foundation.org: fix nommu build]
      Signed-off-by: default avatarJerome Marchand <jmarchan@redhat.com>
      Cc: Dave Hansen <dave.hansen@linux.intel.com>
      Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  3. 13 Jan, 2014 2 commits
    • Peter Zijlstra's avatar
      sched/deadline: Remove the sysctl_sched_dl knobs · 1724813d
      Peter Zijlstra authored
      Remove the deadline specific sysctls for now. The problem with them is
      that the interaction with the exisiting rt knobs is nearly impossible
      to get right.
      The current (as per before this patch) situation is that the rt and dl
      bandwidth is completely separate and we enforce rt+dl < 100%. This is
      undesirable because this means that the rt default of 95% leaves us
      hardly any room, even though dl tasks are saver than rt tasks.
      Another proposed solution was (a discarted patch) to have the dl
      bandwidth be a fraction of the rt bandwidth. This is highly
      confusing imo.
      Furthermore neither proposal is consistent with the situation we
      actually want; which is rt tasks ran from a dl server. In which case
      the rt bandwidth is a direct subset of dl.
      So whichever way we go, the introduction of dl controls at this point
      is painful. Therefore remove them and instead share the rt budget.
      This means that for now the rt knobs are used for dl admission control
      and the dl runtime is accounted against the rt runtime. I realise that
      this isn't entirely desirable either; but whatever we do we appear to
      need to change the interface later, so better have a small interface
      for now.
      Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Link: http://lkml.kernel.org/n/tip-zpyqbqds1r0vyxtxza1e7rdc@git.kernel.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    • Dario Faggioli's avatar
      sched/deadline: Add bandwidth management for SCHED_DEADLINE tasks · 332ac17e
      Dario Faggioli authored
      In order of deadline scheduling to be effective and useful, it is
      important that some method of having the allocation of the available
      CPU bandwidth to tasks and task groups under control.
      This is usually called "admission control" and if it is not performed
      at all, no guarantee can be given on the actual scheduling of the
      -deadline tasks.
      Since when RT-throttling has been introduced each task group have a
      bandwidth associated to itself, calculated as a certain amount of
      runtime over a period. Moreover, to make it possible to manipulate
      such bandwidth, readable/writable controls have been added to both
      procfs (for system wide settings) and cgroupfs (for per-group
      Therefore, the same interface is being used for controlling the
      bandwidth distrubution to -deadline tasks and task groups, i.e.,
      new controls but with similar names, equivalent meaning and with
      the same usage paradigm are added.
      However, more discussion is needed in order to figure out how
      we want to manage SCHED_DEADLINE bandwidth at the task group level.
      Therefore, this patch adds a less sophisticated, but actually
      very sensible, mechanism to ensure that a certain utilization
      cap is not overcome per each root_domain (the single rq for !SMP
      Another main difference between deadline bandwidth management and
      RT-throttling is that -deadline tasks have bandwidth on their own
      (while -rt ones doesn't!), and thus we don't need an higher level
      throttling mechanism to enforce the desired bandwidth.
      This patch, therefore:
       - adds system wide deadline bandwidth management by means of:
          * /proc/sys/kernel/sched_dl_runtime_us,
          * /proc/sys/kernel/sched_dl_period_us,
         that determine (i.e., runtime / period) the total bandwidth
         available on each CPU of each root_domain for -deadline tasks;
       - couples the RT and deadline bandwidth management, i.e., enforces
         that the sum of how much bandwidth is being devoted to -rt
         -deadline tasks to stay below 100%.
      This means that, for a root_domain comprising M CPUs, -deadline tasks
      can be created until the sum of their bandwidths stay below:
          M * (sched_dl_runtime_us / sched_dl_period_us)
      It is also possible to disable this bandwidth management logic, and
      be thus free of oversubscribing the system up to any arbitrary level.
      Signed-off-by: default avatarDario Faggioli <raistlin@linux.it>
      Signed-off-by: default avatarJuri Lelli <juri.lelli@gmail.com>
      Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Link: http://lkml.kernel.org/r/1383831828-15501-12-git-send-email-juri.lelli@gmail.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
  4. 17 Dec, 2013 1 commit
  5. 12 Nov, 2013 1 commit
  6. 16 Oct, 2013 1 commit
  7. 09 Oct, 2013 3 commits
  8. 04 Oct, 2013 1 commit
  9. 23 Sep, 2013 1 commit
  10. 11 Sep, 2013 1 commit
  11. 10 Sep, 2013 1 commit
    • Glauber Costa's avatar
      fs: bump inode and dentry counters to long · 3942c07c
      Glauber Costa authored
      This series reworks our current object cache shrinking infrastructure in
      two main ways:
       * Noticing that a lot of users copy and paste their own version of LRU
         lists for objects, we put some effort in providing a generic version.
         It is modeled after the filesystem users: dentries, inodes, and xfs
         (for various tasks), but we expect that other users could benefit in
         the near future with little or no modification.  Let us know if you
         have any issues.
       * The underlying list_lru being proposed automatically and
         transparently keeps the elements in per-node lists, and is able to
         manipulate the node lists individually.  Given this infrastructure, we
         are able to modify the up-to-now hammer called shrink_slab to proceed
         with node-reclaim instead of always searching memory from all over like
         it has been doing.
      Per-node lru lists are also expected to lead to less contention in the lru
      locks on multi-node scans, since we are now no longer fighting for a
      global lock.  The locks usually disappear from the profilers with this
      Although we have no official benchmarks for this version - be our guest to
      independently evaluate this - earlier versions of this series were
      performance tested (details at
      http://permalink.gmane.org/gmane.linux.kernel.mm/100537) yielding no
      visible performance regressions while yielding a better qualitative
      behavior in NUMA machines.
      With this infrastructure in place, we can use the list_lru entry point to
      provide memcg isolation and per-memcg targeted reclaim.  Historically,
      those two pieces of work have been posted together.  This version presents
      only the infrastructure work, deferring the memcg work for a later time,
      so we can focus on getting this part tested.  You can see more about the
      history of such work at http://lwn.net/Articles/552769/
      Dave Chinner (18):
        dcache: convert dentry_stat.nr_unused to per-cpu counters
        dentry: move to per-sb LRU locks
        dcache: remove dentries from LRU before putting on dispose list
        mm: new shrinker API
        shrinker: convert superblock shrinkers to new API
        list: add a new LRU list type
        inode: convert inode lru list to generic lru list code.
        dcache: convert to use new lru list infrastructure
        list_lru: per-node list infrastructure
        shrinker: add node awareness
        fs: convert inode and dentry shrinking to be node aware
        xfs: convert buftarg LRU to generic code
        xfs: rework buffer dispose list tracking
        xfs: convert dquot cache lru to list_lru
        fs: convert fs shrinkers to new scan/count API
        drivers: convert shrinkers to new count/scan API
        shrinker: convert remaining shrinkers to count/scan API
        shrinker: Kill old ->shrink API.
      Glauber Costa (7):
        fs: bump inode and dentry counters to long
        super: fix calculation of shrinkable objects for small numbers
        list_lru: per-node API
        vmscan: per-node deferred work
        i915: bail out earlier when shrinker cannot acquire mutex
        hugepage: convert huge zero page shrinker to new shrinker API
        list_lru: dynamically adjust node arrays
      This patch:
      There are situations in very large machines in which we can have a large
      quantity of dirty inodes, unused dentries, etc.  This is particularly true
      when umounting a filesystem, where eventually since every live object will
      eventually be discarded.
      Dave Chinner reported a problem with this while experimenting with the
      shrinker revamp patchset.  So we believe it is time for a change.  This
      patch just moves int to longs.  Machines where it matters should have a
      big long anyway.
      Signed-off-by: default avatarGlauber Costa <glommer@openvz.org>
      Cc: Dave Chinner <dchinner@redhat.com>
      Cc: "Theodore Ts'o" <tytso@mit.edu>
      Cc: Adrian Hunter <adrian.hunter@intel.com>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
      Cc: Arve Hjønnevåg <arve@android.com>
      Cc: Carlos Maiolino <cmaiolino@redhat.com>
      Cc: Christoph Hellwig <hch@lst.de>
      Cc: Chuck Lever <chuck.lever@oracle.com>
      Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
      Cc: Dave Chinner <dchinner@redhat.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Gleb Natapov <gleb@redhat.com>
      Cc: Greg Thelen <gthelen@google.com>
      Cc: J. Bruce Fields <bfields@redhat.com>
      Cc: Jan Kara <jack@suse.cz>
      Cc: Jerome Glisse <jglisse@redhat.com>
      Cc: John Stultz <john.stultz@linaro.org>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Kent Overstreet <koverstreet@google.com>
      Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Cc: Marcelo Tosatti <mtosatti@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Steven Whitehouse <swhiteho@redhat.com>
      Cc: Thomas Hellstrom <thellstrom@vmware.com>
      Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
  12. 26 Jul, 2013 1 commit
  13. 23 Jun, 2013 1 commit
    • Dave Hansen's avatar
      perf: Drop sample rate when sampling is too slow · 14c63f17
      Dave Hansen authored
      This patch keeps track of how long perf's NMI handler is taking,
      and also calculates how many samples perf can take a second.  If
      the sample length times the expected max number of samples
      exceeds a configurable threshold, it drops the sample rate.
      This way, we don't have a runaway sampling process eating up the
      This patch can tend to drop the sample rate down to level where
      perf doesn't work very well.  *BUT* the alternative is that my
      system hangs because it spends all of its time handling NMIs.
      I'll take a busted performance tool over an entire system that's
      busted and undebuggable any day.
      BTW, my suspicion is that there's still an underlying bug here.
      Using the HPET instead of the TSC is definitely a contributing
      factor, but I suspect there are some other things going on.
      But, I can't go dig down on a bug like that with my machine
      hanging all the time.
      Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
      Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: paulus@samba.org
      Cc: acme@ghostprotocols.net
      Cc: Dave Hansen <dave@sr71.net>
      [ Prettified it a bit. ]
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
  14. 20 Jun, 2013 1 commit
    • Frederic Weisbecker's avatar
      watchdog: Rename confusing state variable · 3c00ea82
      Frederic Weisbecker authored
      We have two very conflicting state variable names in the
      * watchdog_enabled: This one reflects the user interface. It's
      set to 1 by default and can be overriden with boot options
      or sysctl/procfs interface.
      * watchdog_disabled: This is the internal toggle state that
      tells if watchdog threads, timers and NMI events are currently
      running or not. This state mostly depends on the user settings.
      It's a convenient state latch.
      Now we really need to find clearer names because those
      are just too confusing to encourage deep review.
      watchdog_enabled now becomes watchdog_user_enabled to reflect
      its purpose as an interface.
      watchdog_disabled becomes watchdog_running to suggest its
      role as a pure internal state.
      Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
      Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
      Cc: Anish Singh <anish198519851985@gmail.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Li Zhong <zhong@linux.vnet.ibm.com>
      Cc: Don Zickus <dzickus@redhat.com>
  15. 19 Jun, 2013 1 commit
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Disable tracing on warning · de7edd31
      Steven Rostedt (Red Hat) authored
      Add a traceoff_on_warning option in both the kernel command line as well
      as a sysctl option. When set, any WARN*() function that is hit will cause
      the tracing_on variable to be cleared, which disables writing to the
      ring buffer.
      This is useful especially when tracing a bug with function tracing. When
      a warning is hit, the print caused by the warning can flood the trace with
      the functions that producing the output for the warning. This can make the
      resulting trace useless by either hiding where the bug happened, or worse,
      by overflowing the buffer and losing the trace of the bug totally.
      Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
  16. 28 May, 2013 1 commit
  17. 29 Apr, 2013 3 commits
    • Andrew Shewmaker's avatar
      mm: replace hardcoded 3% with admin_reserve_pages knob · 4eeab4f5
      Andrew Shewmaker authored
      Add an admin_reserve_kbytes knob to allow admins to change the hardcoded
      memory reserve to something other than 3%, which may be multiple
      gigabytes on large memory systems.  Only about 8MB is necessary to
      enable recovery in the default mode, and only a few hundred MB are
      required even when overcommit is disabled.
      admin_reserve_kbytes is initialized to min(3% free pages, 8MB)
      I arrived at 8MB by summing the RSS of sshd or login, bash, and top.
      Please see first patch in this series for full background, motivation,
      testing, and full changelog.
      [akpm@linux-foundation.org: coding-style fixes]
      [akpm@linux-foundation.org: make init_admin_reserve() static]
      Signed-off-by: default avatarAndrew Shewmaker <agshew@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    • Andrew Shewmaker's avatar
      mm: limit growth of 3% hardcoded other user reserve · c9b1d098
      Andrew Shewmaker authored
      Add user_reserve_kbytes knob.
      Limit the growth of the memory reserved for other user processes to
      min(3% current process size, user_reserve_pages).  Only about 8MB is
      necessary to enable recovery in the default mode, and only a few hundred
      MB are required even when overcommit is disabled.
      user_reserve_pages defaults to min(3% free pages, 128MB)
      I arrived at 128MB by taking the max VSZ of sshd, login, bash, and top ...
      then adding the RSS of each.
      This only affects OVERCOMMIT_NEVER mode.
      1. user reserve
      __vm_enough_memory reserves a hardcoded 3% of the current process size for
      other applications when overcommit is disabled.  This was done so that a
      user could recover if they launched a memory hogging process.  Without the
      reserve, a user would easily run into a message such as:
      bash: fork: Cannot allocate memory
      2. admin reserve
      Additionally, a hardcoded 3% of free memory is reserved for root in both
      overcommit 'guess' and 'never' modes.  This was intended to prevent a
      scenario where root-cant-log-in and perform recovery operations.
      Note that this reserve shrinks, and doesn't guarantee a useful reserve.
      The two hardcoded memory reserves should be updated to account for current
      memory sizes.
      Also, the admin reserve would be more useful if it didn't shrink too much.
      When the current code was originally written, 1GB was considered
      "enterprise".  Now the 3% reserve can grow to multiple GB on large memory
      systems, and it only needs to be a few hundred MB at most to enable a user
      or admin to recover a system with an unwanted memory hogging process.
      I've found that reducing these reserves is especially beneficial for a
      specific type of application load:
       * single application system
       * one or few processes (e.g. one per core)
       * allocating all available memory
       * not initializing every page immediately
       * long running
      I've run scientific clusters with this sort of load.  A long running job
      sometimes failed many hours (weeks of CPU time) into a calculation.  They
      weren't initializing all of their memory immediately, and they weren't
      using calloc, so I put systems into overcommit 'never' mode.  These
      clusters run diskless and have no swap.
      However, with the current reserves, a user wishing to allocate as much
      memory as possible to one process may be prevented from using, for
      example, almost 2GB out of 32GB.
      The effect is less, but still significant when a user starts a job with
      one process per core.  I have repeatedly seen a set of processes
      requesting the same amount of memory fail because one of them could not
      allocate the amount of memory a user would expect to be able to allocate.
      For example, Message Passing Interfce (MPI) processes, one per core.  And
      it is similar for other parallel programming frameworks.
      Changing this reserve code will make the overcommit never mode more useful
      by allowing applications to allocate nearly all of the available memory.
      Also, the new admin_reserve_kbytes will be safer than the current behavior
      since the hardcoded 3% of available memory reserve can shrink to something
      useless in the case where applications have grabbed all available memory.
      * "bash: fork: Cannot allocate memory"
        The downside of the first patch-- which creates a tunable user reserve
        that is only used in overcommit 'never' mode--is that an admin can set
        it so low that a user may not be able to kill their process, even if
        they already have a shell prompt.
        Of course, a user can get in the same predicament with the current 3%
        reserve--they just have to launch processes until 3% becomes negligible.
      * root-cant-log-in problem
        The second patch, adding the tunable rootuser_reserve_pages, allows
        the admin to shoot themselves in the foot by setting it too small.  They
        can easily get the system into a state where root-can't-log-in.
        However, the new admin_reserve_kbytes will be safer than the current
        behavior since the hardcoded 3% of available memory reserve can shrink
        to something useless in the case where applications have grabbed all
        available memory.
       * Memory cgroups provide a more flexible way to limit application memory.
         Not everyone wants to set up cgroups or deal with their overhead.
       * We could create a fourth overcommit mode which provides smaller reserves.
         The size of useful reserves may be drastically different depending
         on the whether the system is embedded or enterprise.
       * Force users to initialize all of their memory or use calloc.
         Some users don't want/expect the system to overcommit when they malloc.
         Overcommit 'never' mode is for this scenario, and it should work well.
      The new user and admin reserve tunables are simple to use, with low
      overhead compared to cgroups.  The patches preserve current behavior where
      3% of memory is less than 128MB, except that the admin reserve doesn't
      shrink to an unusable size under pressure.  The code allows admins to tune
      for embedded and enterprise usage.
       * How is the root-cant-login problem addressed?
         What happens if admin_reserve_pages is set to 0?
         Root is free to shoot themselves in the foot by setting
         admin_reserve_kbytes too low.
         On x86_64, the minimum useful reserve is:
           8MB for overcommit 'guess'
         128MB for overcommit 'never'
         admin_reserve_pages defaults to min(3% free memory, 8MB)
         So, anyone switching to 'never' mode needs to adjust
       * How do you calculate a minimum useful reserve?
         A user or the admin needs enough memory to login and perform
         recovery operations, which includes, at a minimum:
         sshd or login + bash (or some other shell) + top (or ps, kill, etc.)
         For overcommit 'guess', we can sum resident set sizes (RSS)
         because we only need enough memory to handle what the recovery
         programs will typically use. On x86_64 this is about 8MB.
         For overcommit 'never', we can take the max of their virtual sizes (VSZ)
         and add the sum of their RSS. We use VSZ instead of RSS because mode
         forces us to ensure we can fulfill all of the requested memory allocations--
         even if the programs only use a fraction of what they ask for.
         On x86_64 this is about 128MB.
         When swap is enabled, reserves are useful even when they are as
         small as 10MB, regardless of overcommit mode.
         When both swap and overcommit are disabled, then the admin should
         tune the reserves higher to be absolutley safe. Over 230MB each
         was safest in my testing.
       * What happens if user_reserve_pages is set to 0?
         Note, this only affects overcomitt 'never' mode.
         Then a user will be able to allocate all available memory minus
         However, they will easily see a message such as:
         "bash: fork: Cannot allocate memory"
         And they won't be able to recover/kill their application.
         The admin should be able to recover the system if
         admin_reserve_kbytes is set appropriately.
       * What's the difference between overcommit 'guess' and 'never'?
         "Guess" allows an allocation if there are enough free + reclaimable
         pages. It has a hardcoded 3% of free pages reserved for root.
         "Never" allows an allocation if there is enough swap + a configurable
         percentage (default is 50) of physical RAM. It has a hardcoded 3% of
         free pages reserved for root, like "Guess" mode. It also has a
         hardcoded 3% of the current process size reserved for additional
       * Why is overcommit 'guess' not suitable even when an app eventually
         writes to every page? It takes free pages, file pages, available
         swap pages, reclaimable slab pages into consideration. In other words,
         these are all pages available, then why isn't overcommit suitable?
         Because it only looks at the present state of the system. It
         does not take into account the memory that other applications have
         malloced, but haven't initialized yet. It overcommits the system.
      Test Summary
      There was little change in behavior in the default overcommit 'guess'
      mode with swap enabled before and after the patch. This was expected.
      Systems run most predictably (i.e. no oom kills) in overcommit 'never'
      mode with swap enabled. This also allowed the most memory to be allocated
      to a user application.
      Overcommit 'guess' mode without swap is a bad idea. It is easy to
      crash the system. None of the other tested combinations crashed.
      This matches my experience on the Roadrunner supercomputer.
      Without the tunable user reserve, a system in overcommit 'never' mode
      and without swap does not allow the admin to recover, although the
      admin can.
      With the new tunable reserves, a system in overcommit 'never' mode
      and without swap can be configured to:
      1. maximize user-allocatable memory, running close to the edge of
      2. maximize recoverability, sacrificing allocatable memory to
      ensure that a user cannot take down a system
      Test Description
      Fedora 18 VM - 4 x86_64 cores, 5725MB RAM, 4GB Swap
      System is booted into multiuser console mode, with unnecessary services
      turned off. Caches were dropped before each test.
      Hogs are user memtester processes that attempt to allocate all free memory
      as reported by /proc/meminfo
      In overcommit 'never' mode, memory_ratio=100
      Test Results
      Overcommit | Swap | Hogs | MB Got/Wanted | OOMs | User Recovery | Admin Recovery
      ----------   ----   ----   -------------   ----   -------------   --------------
      guess        yes    1      5432/5432       no     yes             yes
      guess        yes    4      5444/5444       1      yes             yes
      guess        no     1      5302/5449       no     yes             yes
      guess        no     4      -               crash  no              no
      never        yes    1      5460/5460       1      yes             yes
      never        yes    4      5460/5460       1      yes             yes
      never        no     1      5218/5432       no     no              yes
      never        no     4      5203/5448       no     no              yes
      User and Admin Recovery show their respective reserves, if applicable.
      Overcommit | Swap | Hogs | MB Got/Wanted | OOMs | User Recovery | Admin Recovery
      ----------   ----   ----   -------------   ----   -------------   --------------
      guess        yes    1      5419/5419       no     - yes           8MB yes
      guess        yes    4      5436/5436       1      - yes           8MB yes
      guess        no     1      5440/5440       *      - yes           8MB yes
      guess        no     4      -               crash  - no            8MB no
      * process would successfully mlock, then the oom killer would pick it
      never        yes    1      5446/5446       no     10MB yes        20MB yes
      never        yes    4      5456/5456       no     10MB yes        20MB yes
      never        no     1      5387/5429       no     128MB no        8MB barely
      never        no     1      5323/5428       no     226MB barely    8MB barely
      never        no     1      5323/5428       no     226MB barely    8MB barely
      never        no     1      5359/5448       no     10MB no         10MB barely
      never        no     1      5323/5428       no     0MB no          10MB barely
      never        no     1      5332/5428       no     0MB no          50MB yes
      never        no     1      5293/5429       no     0MB no          90MB yes
      never        no     1      5001/5427       no     230MB yes       338MB yes
      never        no     4*     4998/5424       no     230MB yes       338MB yes
      * more memtesters were launched, able to allocate approximately another 100MB
      Future Work
       - Test larger memory systems.
       - Test an embedded image.
       - Test other architectures.
       - Time malloc microbenchmarks.
       - Would it be useful to be able to set overcommit policy for
         each memory cgroup?
       - Some lines are slightly above 80 chars.
         Perhaps define a macro to convert between pages and kb?
         Other places in the kernel do this.
      [akpm@linux-foundation.org: coding-style fixes]
      [akpm@linux-foundation.org: make init_user_reserve() static]
      Signed-off-by: default avatarAndrew Shewmaker <agshew@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    • Josh Triplett's avatar
      fs: don't compile in drop_caches.c when CONFIG_SYSCTL=n · 146732ce
      Josh Triplett authored
      drop_caches.c provides code only invokable via sysctl, so don't compile it
      in when CONFIG_SYSCTL=n.
      Signed-off-by: default avatarJosh Triplett <josh@joshtriplett.org>
      Acked-by: default avatarKees Cook <keescook@chromium.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  18. 27 Feb, 2013 1 commit
  19. 23 Feb, 2013 1 commit
  20. 15 Feb, 2013 1 commit
  21. 07 Feb, 2013 2 commits
  22. 20 Jan, 2013 1 commit
  23. 09 Jan, 2013 1 commit
  24. 11 Dec, 2012 5 commits
    • Mel Gorman's avatar
      mm: sched: Adapt the scanning rate if a NUMA hinting fault does not migrate · b8593bfd
      Mel Gorman authored
      The PTE scanning rate and fault rates are two of the biggest sources of
      system CPU overhead with automatic NUMA placement.  Ideally a proper policy
      would detect if a workload was properly placed, schedule and adjust the
      PTE scanning rate accordingly. We do not track the necessary information
      to do that but we at least know if we migrated or not.
      This patch scans slower if a page was not migrated as the result of a
      NUMA hinting fault up to sysctl_numa_balancing_scan_period_max which is
      now higher than the previous default. Once every minute it will reset
      the scanner in case of phase changes.
      This is hilariously crude and the numbers are arbitrary. Workloads will
      converge quite slowly in comparison to what a proper policy should be able
      to do. On the plus side, we will chew up less CPU for workloads that have
      no need for automatic balancing.
      Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
    • Peter Zijlstra's avatar
      mm: sched: numa: Implement slow start for working set sampling · 4b96a29b
      Peter Zijlstra authored
      Add a 1 second delay before starting to scan the working set of
      a task and starting to balance it amongst nodes.
      [ note that before the constant per task WSS sampling rate patch
        the initial scan would happen much later still, in effect that
        patch caused this regression. ]
      The theory is that short-run tasks benefit very little from NUMA
      placement: they come and go, and they better stick to the node
      they were started on. As tasks mature and rebalance to other CPUs
      and nodes, so does their NUMA placement have to change and so
      does it start to matter more and more.
      In practice this change fixes an observable kbuild regression:
         # [ a perf stat --null --repeat 10 test of ten bzImage builds to /dev/shm ]
         45.291088843 seconds time elapsed                                          ( +-  0.40% )
         45.154231752 seconds time elapsed                                          ( +-  0.36% )
         +NUMA, no slow start:
         46.172308123 seconds time elapsed                                          ( +-  0.30% )
         46.343168745 seconds time elapsed                                          ( +-  0.25% )
         +NUMA, 1 sec slow start:
         45.224189155 seconds time elapsed                                          ( +-  0.25% )
         45.160866532 seconds time elapsed                                          ( +-  0.17% )
      and it also fixes an observable perf bench (hackbench) regression:
         # perf stat --null --repeat 10 perf bench sched messaging
         -NUMA:                  0.246225691 seconds time elapsed                   ( +-  1.31% )
         +NUMA no slow start:    0.252620063 seconds time elapsed                   ( +-  1.13% )
         +NUMA 1sec delay:       0.248076230 seconds time elapsed                   ( +-  1.35% )
      The implementation is simple and straightforward, most of the patch
      deals with adding the /proc/sys/kernel/numa_balancing_scan_delay_ms tunable
      Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      [ Wrote the changelog, ran measurements, tuned the default. ]
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
      Reviewed-by: default avatarRik van Riel <riel@redhat.com>
    • Peter Zijlstra's avatar
      mm: sched: numa: Implement constant, per task Working Set Sampling (WSS) rate · 6e5fb223
      Peter Zijlstra authored
      Previously, to probe the working set of a task, we'd use
      a very simple and crude method: mark all of its address
      space PROT_NONE.
      That method has various (obvious) disadvantages:
       - it samples the working set at dissimilar rates,
         giving some tasks a sampling quality advantage
         over others.
       - creates performance problems for tasks with very
         large working sets
       - over-samples processes with large address spaces but
         which only very rarely execute
      Improve that method by keeping a rotating offset into the
      address space that marks the current position of the scan,
      and advance it by a constant rate (in a CPU cycles execution
      proportional manner). If the offset reaches the last mapped
      address of the mm then it then it starts over at the first
      The per-task nature of the working set sampling functionality in this tree
      allows such constant rate, per task, execution-weight proportional sampling
      of the working set, with an adaptive sampling interval/frequency that
      goes from once per 100ms up to just once per 8 seconds.  The current
      sampling volume is 256 MB per interval.
      As tasks mature and converge their working set, so does the
      sampling rate slow down to just a trickle, 256 MB per 8
      seconds of CPU time executed.
      This, beyond being adaptive, also rate-limits rarely
      executing systems and does not over-sample on overloaded
      [ In AutoNUMA speak, this patch deals with the effective sampling
        rate of the 'hinting page fault'. AutoNUMA's scanning is
        currently rate-limited, but it is also fundamentally
        single-threaded, executing in the knuma_scand kernel thread,
        so the limit in AutoNUMA is global and does not scale up with
        the number of CPUs, nor does it scan tasks in an execution
        proportional manner.
        So the idea of rate-limiting the scanning was first implemented
        in the AutoNUMA tree via a global rate limit. This patch goes
        beyond that by implementing an execution rate proportional
        working set sampling rate that is not implemented via a single
        global scanning daemon. ]
      [ Dan Carpenter pointed out a possible NULL pointer dereference in the
        first version of this patch. ]
      Based-on-idea-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Bug-Found-By: default avatarDan Carpenter <dan.carpenter@oracle.com>
      Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      [ Wrote changelog and fixed bug. ]
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
      Reviewed-by: default avatarRik van Riel <riel@redhat.com>
    • Peter Zijlstra's avatar
      mm: numa: Add fault driven placement and migration · cbee9f88
      Peter Zijlstra authored
      NOTE: This patch is based on "sched, numa, mm: Add fault driven
      	placement and migration policy" but as it throws away all the policy
      	to just leave a basic foundation I had to drop the signed-offs-by.
      This patch creates a bare-bones method for setting PTEs pte_numa in the
      context of the scheduler that when faulted later will be faulted onto the
      node the CPU is running on.  In itself this does nothing useful but any
      placement policy will fundamentally depend on receiving hints on placement
      from fault context and doing something intelligent about it.
      Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
      Acked-by: default avatarRik van Riel <riel@redhat.com>
    • Ingo Molnar's avatar
      Revert "sched/autogroup: Fix crash on reboot when autogroup is disabled" · c1ad41f1
      Ingo Molnar authored
      This reverts commit 5258f386,
      because the underlying autogroups bug got fixed upstream in
      a better way, via:
        fd8ef117 Revert "sched, autogroup: Stop going ahead if autogroup is disabled"
      Cc: Mike Galbraith <efault@gmx.de>
      Cc: Yong Zhang <yong.zhang0@gmail.com>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
  25. 28 Nov, 2012 1 commit
  26. 30 Oct, 2012 1 commit
    • Mike Galbraith's avatar
      sched/autogroup: Fix crash on reboot when autogroup is disabled · 5258f386
      Mike Galbraith authored
      Due to these two commits:
        8323f26c sched: Fix race in task_group()
        800d4d30 sched, autogroup: Stop going ahead if autogroup is disabled
      ... autogroup scheduling's dynamic knobs are wrecked.
      With both patches applied, all you have to do to crash a box is
      disable autogroup during boot up, then reboot.. boom, NULL pointer
      dereference due to 800d4d30 not allowing autogroup to move things,
      and 8323f26c making that the only way to switch runqueues.
      Remove most of the (dysfunctional) knobs and turn the remaining
      sched_autogroup_enabled knob readonly.
      If the user fiddles with cgroups hereafter, once tasks
      are moved, autogroup won't mess with them again unless
      they call setsid().
      No knobs, no glitz, nada, just a cute little thing folks can
      turn on if they don't want to muck about with cgroups and/or
      Signed-off-by: default avatarMike Galbraith <efault@gmx.de>
      Cc: Xiaotian Feng <xtfeng@gmail.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Xiaotian Feng <dannyfeng@tencent.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: <stable@vger.kernel.org> # v3.6
      Link: http://lkml.kernel.org/r/1351451963.4999.8.camel@maggy.simpson.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
  27. 09 Oct, 2012 1 commit
  28. 05 Oct, 2012 1 commit
  29. 17 Sep, 2012 1 commit
  30. 04 Sep, 2012 1 commit