1. 27 Sep, 2012 3 commits
  2. 01 Aug, 2012 1 commit
  3. 31 May, 2012 1 commit
  4. 21 Apr, 2012 3 commits
  5. 28 Mar, 2012 1 commit
  6. 04 Jan, 2012 1 commit
  7. 13 Jan, 2011 2 commits
  8. 07 Jan, 2011 3 commits
    • Nick Piggin's avatar
      fs: scale mntget/mntput · b3e19d92
      Nick Piggin authored
      
      
      The problem that this patch aims to fix is vfsmount refcounting scalability.
      We need to take a reference on the vfsmount for every successful path lookup,
      which often go to the same mount point.
      
      The fundamental difficulty is that a "simple" reference count can never be made
      scalable, because any time a reference is dropped, we must check whether that
      was the last reference. To do that requires communication with all other CPUs
      that may have taken a reference count.
      
      We can make refcounts more scalable in a couple of ways, involving keeping
      distributed counters, and checking for the global-zero condition less
      frequently.
      
      - check the global sum once every interval (this will delay zero detection
        for some interval, so it's probably a showstopper for vfsmounts).
      
      - keep a local count and only taking the global sum when local reaches 0 (this
        is difficult for vfsmounts, because we can't hold preempt off for the life of
        a reference, so a counter would need to be per-thread or tied strongly to a
        particular CPU which requires more locking).
      
      - keep a local difference of increments and decrements, which allows us to sum
        the total difference and hence find the refcount when summing all CPUs. Then,
        keep a single integer "long" refcount for slow and long lasting references,
        and only take the global sum of local counters when the long refcount is 0.
      
      This last scheme is what I implemented here. Attached mounts and process root
      and working directory references are "long" references, and everything else is
      a short reference.
      
      This allows scalable vfsmount references during path walking over mounted
      subtrees and unattached (lazy umounted) mounts with processes still running
      in them.
      
      This results in one fewer atomic op in the fastpath: mntget is now just a
      per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
      and non-atomic decrement in the common case. However code is otherwise bigger
      and heavier, so single threaded performance is basically a wash.
      Signed-off-by: default avatarNick Piggin <npiggin@kernel.dk>
      b3e19d92
    • Nick Piggin's avatar
      fs: dcache reduce branches in lookup path · fb045adb
      Nick Piggin authored
      
      
      Reduce some branches and memory accesses in dcache lookup by adding dentry
      flags to indicate common d_ops are set, rather than having to check them.
      This saves a pointer memory access (dentry->d_op) in common path lookup
      situations, and saves another pointer load and branch in cases where we
      have d_op but not the particular operation.
      
      Patched with:
      
      git grep -E '[.>]([[:space:]])*d_op([[:space:]])*=' | xargs sed -e 's/\([^\t ]*\)->d_op = \(.*\);/d_set_d_op(\1, \2);/' -e 's/\([^\t ]*\)\.d_op = \(.*\);/d_set_d_op(\&\1, \2);/' -i
      Signed-off-by: default avatarNick Piggin <npiggin@kernel.dk>
      fb045adb
    • Nick Piggin's avatar
      fs: change d_delete semantics · fe15ce44
      Nick Piggin authored
      
      
      Change d_delete from a dentry deletion notification to a dentry caching
      advise, more like ->drop_inode. Require it to be constant and idempotent,
      and not take d_lock. This is how all existing filesystems use the callback
      anyway.
      
      This makes fine grained dentry locking of dput and dentry lru scanning
      much simpler.
      Signed-off-by: default avatarNick Piggin <npiggin@kernel.dk>
      fe15ce44
  9. 28 Dec, 2010 1 commit
  10. 29 Oct, 2010 1 commit
  11. 23 Sep, 2010 1 commit
  12. 11 Aug, 2010 1 commit
  13. 21 Jul, 2010 1 commit
  14. 06 Jul, 2010 1 commit
  15. 30 Mar, 2010 1 commit
    • Tejun Heo's avatar
      include cleanup: Update gfp.h and slab.h includes to prepare for breaking... · 5a0e3ad6
      Tejun Heo authored
      include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
      
      percpu.h is included by sched.h and module.h and thus ends up being
      included when building most .c files.  percpu.h includes slab.h which
      in turn includes gfp.h making everything defined by the two files
      universally available and complicating inclusion dependencies.
      
      percpu.h -> slab.h dependency is about to be removed.  Prepare for
      this change by updating users of gfp and slab facilities include those
      headers directly instead of assuming availability.  As this conversion
      needs to touch large number of source files, the following script is
      used as the basis of conversion.
      
        http://userweb.kernel.org/~tj/misc/slabh-sweep.py
      
      
      
      The script does the followings.
      
      * Scan files for gfp and slab usages and update includes such that
        only the necessary includes are there.  ie. if only gfp is used,
        gfp.h, if slab is used, slab.h.
      
      * When the script inserts a new include, it looks at the include
        blocks and try to put the new include such that its order conforms
        to its surrounding.  It's put in the include block which contains
        core kernel includes, in the same order that the rest are ordered -
        alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
        doesn't seem to be any matching order.
      
      * If the script can't find a place to put a new include (mostly
        because the file doesn't have fitting include block), it prints out
        an error message indicating which .h file needs to be added to the
        file.
      
      The conversion was done in the following steps.
      
      1. The initial automatic conversion of all .c files updated slightly
         over 4000 files, deleting around 700 includes and adding ~480 gfp.h
         and ~3000 slab.h inclusions.  The script emitted errors for ~400
         files.
      
      2. Each error was manually checked.  Some didn't need the inclusion,
         some needed manual addition while adding it to implementation .h or
         embedding .c file was more appropriate for others.  This step added
         inclusions to around 150 files.
      
      3. The script was run again and the output was compared to the edits
         from #2 to make sure no file was left behind.
      
      4. Several build tests were done and a couple of problems were fixed.
         e.g. lib/decompress_*.c used malloc/free() wrappers around slab
         APIs requiring slab.h to be added manually.
      
      5. The script was run on all .h files but without automatically
         editing them as sprinkling gfp.h and slab.h inclusions around .h
         files could easily lead to inclusion dependency hell.  Most gfp.h
         inclusion directives were ignored as stuff from gfp.h was usually
         wildly available and often used in preprocessor macros.  Each
         slab.h inclusion directive was examined and added manually as
         necessary.
      
      6. percpu.h was updated not to include slab.h.
      
      7. Build test were done on the following configurations and failures
         were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
         distributed build env didn't work with gcov compiles) and a few
         more options had to be turned off depending on archs to make things
         build (like ipr on powerpc/64 which failed due to missing writeq).
      
         * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
         * powerpc and powerpc64 SMP allmodconfig
         * sparc and sparc64 SMP allmodconfig
         * ia64 SMP allmodconfig
         * s390 SMP allmodconfig
         * alpha SMP allmodconfig
         * um on x86_64 SMP allmodconfig
      
      8. percpu.h modifications were reverted so that it could be applied as
         a separate patch and serve as bisection point.
      
      Given the fact that I had only a couple of failures from tests on step
      6, I'm fairly confident about the coverage of this conversion patch.
      If there is a breakage, it's likely to be something in one of the arch
      headers which should be easily discoverable easily on most builds of
      the specific arch.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Guess-its-ok-by: default avatarChristoph Lameter <cl@linux-foundation.org>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
      5a0e3ad6
  16. 06 Mar, 2010 1 commit
    • Rik van Riel's avatar
      mm: change anon_vma linking to fix multi-process server scalability issue · 5beb4930
      Rik van Riel authored
      
      
      The old anon_vma code can lead to scalability issues with heavily forking
      workloads.  Specifically, each anon_vma will be shared between the parent
      process and all its child processes.
      
      In a workload with 1000 child processes and a VMA with 1000 anonymous
      pages per process that get COWed, this leads to a system with a million
      anonymous pages in the same anon_vma, each of which is mapped in just one
      of the 1000 processes.  However, the current rmap code needs to walk them
      all, leading to O(N) scanning complexity for each page.
      
      This can result in systems where one CPU is walking the page tables of
      1000 processes in page_referenced_one, while all other CPUs are stuck on
      the anon_vma lock.  This leads to catastrophic failure for a benchmark
      like AIM7, where the total number of processes can reach in the tens of
      thousands.  Real workloads are still a factor 10 less process intensive
      than AIM7, but they are catching up.
      
      This patch changes the way anon_vmas and VMAs are linked, which allows us
      to associate multiple anon_vmas with a VMA.  At fork time, each child
      process gets its own anon_vmas, in which its COWed pages will be
      instantiated.  The parents' anon_vma is also linked to the VMA, because
      non-COWed pages could be present in any of the children.
      
      This reduces rmap scanning complexity to O(1) for the pages of the 1000
      child processes, with O(N) complexity for at most 1/N pages in the system.
       This reduces the average scanning cost in heavily forking workloads from
      O(N) to 2.
      
      The only real complexity in this patch stems from the fact that linking a
      VMA to anon_vmas now involves memory allocations.  This means vma_adjust
      can fail, if it needs to attach a VMA to anon_vma structures.  This in
      turn means error handling needs to be added to the calling functions.
      
      A second source of complexity is that, because there can be multiple
      anon_vmas, the anon_vma linking in vma_adjust can no longer be done under
      "the" anon_vma lock.  To prevent the rmap code from walking up an
      incomplete VMA, this patch introduces the VM_LOCK_RMAP VMA flag.  This bit
      flag uses the same slot as the NOMMU VM_MAPPED_COPY, with an ifdef in mm.h
      to make sure it is impossible to compile a kernel that needs both symbolic
      values for the same bitflag.
      
      Some test results:
      
      Without the anon_vma changes, when AIM7 hits around 9.7k users (on a test
      box with 16GB RAM and not quite enough IO), the system ends up running
      >99% in system time, with every CPU on the same anon_vma lock in the
      pageout code.
      
      With these changes, AIM7 hits the cross-over point around 29.7k users.
      This happens with ~99% IO wait time, there never seems to be any spike in
      system time.  The anon_vma lock contention appears to be resolved.
      
      [akpm@linux-foundation.org: cleanups]
      Signed-off-by: default avatarRik van Riel <riel@redhat.com>
      Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
      Cc: Larry Woodman <lwoodman@redhat.com>
      Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
      Cc: Minchan Kim <minchan.kim@gmail.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      5beb4930
  17. 26 Feb, 2010 1 commit
  18. 06 Jan, 2010 1 commit
  19. 16 Dec, 2009 1 commit
  20. 04 Dec, 2009 1 commit
  21. 18 Nov, 2009 1 commit
  22. 12 Nov, 2009 1 commit
  23. 30 Jun, 2009 1 commit
    • Jan Beulich's avatar
      [IA64] address compiler warnings perfmon.c/salinfo.c · fa276f36
      Jan Beulich authored
      
      
      perfmon.c has a dubious cast directly from "int" to "void *". Add
      an intermediate cast to "long" to keep gcc happy.
      
      salinfo.c uses "down_trylock()" in a highly creative way (explained
      in the comments in the file) ... but it does kick out this warning:
      
       arch/ia64/kernel/salinfo.c:195: warning: ignoring return value of 'down_trylock'
      
      which people occasionally try to "fix" in ways that do not work. Use some
      casts to keep gcc quiet.
      Signed-off-by: default avatarJan Beulich <jbeulich@novell.com>
      Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
      fa276f36
  24. 17 Jun, 2009 2 commits
    • Matthew Wilcox's avatar
      [IA64] Convert ia64 to use int-ll64.h · e088a4ad
      Matthew Wilcox authored
      
      
      It is generally agreed that it would be beneficial for u64 to be an
      unsigned long long on all architectures.  ia64 (in common with several
      other 64-bit architectures) currently uses unsigned long.  Migrating
      piecemeal is too painful; this giant patch fixes all compilation warnings
      and errors that come as a result of switching to use int-ll64.h.
      
      Note that userspace will still see __u64 defined as unsigned long.  This
      is important as it affects C++ name mangling.
      
      [Updated by Tony Luck to change efi.h:efi_freemem_callback_t to use
       u64 for start/end rather than unsigned long]
      Signed-off-by: default avatarMatthew Wilcox <willy@linux.intel.com>
      Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
      e088a4ad
    • Thomas Gleixner's avatar
      remove put_cpu_no_resched() · 8b0b1db0
      Thomas Gleixner authored
      
      
      put_cpu_no_resched() is an optimization of put_cpu() which unfortunately
      can cause high latencies.
      
      The nfs iostats code uses put_cpu_no_resched() in a code sequence where a
      reschedule request caused by an interrupt between the get_cpu() and the
      put_cpu_no_resched() can delay the reschedule for at least HZ.
      
      The other users of put_cpu_no_resched() optimize correctly in interrupt
      code, but there is no real harm in using the put_cpu() function which is
      an alias for preempt_enable().  The extra check of the preemmpt count is
      not as critical as the potential source of missing a reschedule.
      
      Debugged in the preempt-rt tree and verified in mainline.
      
      Impact: remove a high latency source
      
      [akpm@linux-foundation.org: build fix]
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Acked-by: default avatarIngo Molnar <mingo@elte.hu>
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
      Cc: "J. Bruce Fields" <bfields@fieldses.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      8b0b1db0
  25. 27 Mar, 2009 1 commit
  26. 16 Mar, 2009 1 commit
  27. 13 Nov, 2008 2 commits
  28. 01 Nov, 2008 1 commit
    • Al Viro's avatar
      saner FASYNC handling on file close · 233e70f4
      Al Viro authored
      
      
      As it is, all instances of ->release() for files that have ->fasync()
      need to remember to evict file from fasync lists; forgetting that
      creates a hole and we actually have a bunch that *does* forget.
      
      So let's keep our lives simple - let __fput() check FASYNC in
      file->f_flags and call ->fasync() there if it's been set.  And lose that
      crap in ->release() instances - leaving it there is still valid, but we
      don't have to bother anymore.
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      233e70f4
  29. 06 Oct, 2008 1 commit
  30. 26 Jul, 2008 1 commit
  31. 26 Jun, 2008 1 commit