1. 30 Apr, 2013 8 commits
  2. 29 Apr, 2013 3 commits
    • Anton Vorontsov's avatar
      memcg: add memory.pressure_level events · 70ddf637
      Anton Vorontsov authored
      With this patch userland applications that want to maintain the
      interactivity/memory allocation cost can use the pressure level
      notifications.  The levels are defined like this:
      
      The "low" level means that the system is reclaiming memory for new
      allocations.  Monitoring this reclaiming activity might be useful for
      maintaining cache level.  Upon notification, the program (typically
      "Activity Manager") might analyze vmstat and act in advance (i.e.
      prematurely shutdown unimportant services).
      
      The "medium" level means that the system is experiencing medium memory
      pressure, the system might be making swap, paging out active file
      caches, etc.  Upon this event applications may decide to further analyze
      vmstat/zoneinfo/memcg or internal memory usage statistics and free any
      resources that can be easily reconstructed or re-read from a disk.
      
      The "critical" level means that the system is actively thrashing, it is
      about to out of memory (OOM) or even the in-kernel OOM killer is...
      70ddf637
    • 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.
      
      This affects OVERCOMMIT_GUESS and OVERCOMMIT_NEVER.
      
      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>
      4eeab4f5
    • 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.
      
      Background
      
      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.
      
      Motivation
      
      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.
      
      Risks
      
      * "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.
      
      Alternatives
      
       * 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.
      
      FAQ
      
       * 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
         admin_reserve_pages.
      
       * 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
         admin_reserve_kbytes.
      
         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
         applications.
      
       * 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
      recoverability
      
      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
      
      3.9.0-rc1-mm1
      
      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
      
      3.9.0-rc1-mm1-tunablereserves
      
      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>
      c9b1d098
  3. 23 Apr, 2013 2 commits
  4. 21 Apr, 2013 1 commit
  5. 17 Apr, 2013 5 commits
  6. 15 Apr, 2013 1 commit
  7. 13 Apr, 2013 1 commit
  8. 09 Apr, 2013 1 commit
  9. 08 Apr, 2013 15 commits
  10. 06 Apr, 2013 1 commit
  11. 04 Apr, 2013 2 commits
    • Takashi Iwai's avatar
      Revert "ALSA: hda - Allow power_save_controller option override DCAPS" · 8fc24426
      Takashi Iwai authored
      This reverts commit 6ab31741.
      
      The commit [6ab31741: ALSA: hda - Allow power_save_controller option
      override DCAPS] changed the behavior of power_save_controller so that
      it can override the driver capability.  This assumed that this option
      is rarely changed dynamically unlike power_save option.  Too naive.
      
      It turned out that the user-space power-management tool tries to set
      power_save_controller option to 1 together with power_save option
      without knowing what's actually doing.  This enabled forcibly the
      runtime PM of the controller,  which is known to be broken om many
      chips thus disabled as default.
      
      So, the only sane fix is to revert this commit again.  It was intended
      to ease debugging/testing for runtime PM enablement, but obviously we
      need another way for it.
      
      Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=56171
      
      Reported-and-tested-by: default avatarNikita Tsukanov <keks9n@gmail.com>
      Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      8fc24426
    • Tony Prisk's avatar
      video: fb: vt8500: Convert framebuffer drivers to standardized binding · 7ab0a484
      Tony Prisk authored
      
      
      Now that a display timing binding is available, convert our almost identical
      binding to use the standard binding.
      
      This patch converts the vt8500 and wm8505 framebuffer drivers and
      associated dts/dtsi files to use the standard binding as defined in
      bindings/video/display-timing.txt.
      
      There are two side-effects of making this conversion:
      
      1) The fb node should now be in the board file, rather than the soc file as
      the display-timing node is a child of the fb node.
      
      2) We still require a bits per pixel property to initialize the framebuffer
      for the different lcd panels. Rather than including this as part of the
      display timing, it is moved into the framebuffer node.
      
      I have also taken the opportunity to alphabetise the includes of each
      driver to avoid double-ups.
      Signed-off-by: default avatarTony Prisk <linux@prisktech.co.nz>
      Signed-off-by: default avatarTomi Valkeinen <tomi.valkeinen@ti.com>
      7ab0a484