Eric Lee / linux-smarc-t335x-v3.2

11 Dec, 2008

3 commits

  • 02d211688   revert "percpu_counter: new function percpu_counter_sum_and_set" ... Browse Code »

    Revert

    commit e8ced39d5e8911c662d4d69a342b9d053eaaac4e
    Author: Mingming Cao
    Date: Fri Jul 11 19:27:31 2008 -0400

    percpu_counter: new function percpu_counter_sum_and_set

    As described in

    revert "percpu counter: clean up percpu_counter_sum_and_set()"

    the new percpu_counter_sum_and_set() is racy against updates to the
    cpu-local accumulators on other CPUs. Revert that change.

    This means that ext4 will be slow again. But correct.

    Reported-by: Eric Dumazet
    Cc: "David S. Miller"
    Cc: Peter Zijlstra
    Cc: Mingming Cao
    Cc:
    Cc: [2.6.27.x]
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Andrew Morton
     
  • 71c5576fb   revert "percpu counter: clean up percpu_counter_sum_and_set()" ... Browse Code »

    Revert

    commit 1f7c14c62ce63805f9574664a6c6de3633d4a354
    Author: Mingming Cao
    Date: Thu Oct 9 12:50:59 2008 -0400

    percpu counter: clean up percpu_counter_sum_and_set()

    Before this patch we had the following:

    percpu_counter_sum(): return the percpu_counter's value

    percpu_counter_sum_and_set(): return the percpu_counter's value, copying
    that value into the central value and zeroing the per-cpu counters before
    returning.

    After this patch, percpu_counter_sum_and_set() has gone, and
    percpu_counter_sum() gets the old percpu_counter_sum_and_set()
    functionality.

    Problem is, as Eric points out, the old percpu_counter_sum_and_set()
    functionality was racy and wrong. It zeroes out counters on "other" cpus,
    without holding any locks which will prevent races agaist updates from
    those other CPUS.

    This patch reverts 1f7c14c62ce63805f9574664a6c6de3633d4a354. This means
    that percpu_counter_sum_and_set() still has the race, but
    percpu_counter_sum() does not.

    Note that this is not a simple revert - ext4 has since started using
    percpu_counter_sum() for its dirty_blocks counter as well.

    Note that this revert patch changes percpu_counter_sum() semantics.

    Before the patch, a call to percpu_counter_sum() will bring the counter's
    central counter mostly up-to-date, so a following percpu_counter_read()
    will return a close value.

    After this patch, a call to percpu_counter_sum() will leave the counter's
    central accumulator unaltered, so a subsequent call to
    percpu_counter_read() can now return a significantly inaccurate result.

    If there is any code in the tree which was introduced after
    e8ced39d5e8911c662d4d69a342b9d053eaaac4e was merged, and which depends
    upon the new percpu_counter_sum() semantics, that code will break.

    Reported-by: Eric Dumazet
    Cc: "David S. Miller"
    Cc: Peter Zijlstra
    Cc: Mingming Cao
    Cc:
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Andrew Morton
     
  • fd3d664fe   percpu_counter: fix CPU unplug race in percpu_counter_destroy() ... Browse Code »

    We should first delete the counter from percpu_counters list
    before freeing memory, or a percpu_counter_hotcpu_callback()
    could dereference a NULL pointer.

    Signed-off-by: Eric Dumazet
    Acked-by: David S. Miller
    Cc: Peter Zijlstra
    Cc: Mingming Cao
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Eric Dumazet
     

10 Oct, 2008

1 commit

  • 1f7c14c62   percpu counter: clean up percpu_counter_sum_and_set() ... Browse Code »

    percpu_counter_sum_and_set() and percpu_counter_sum() is the same except
    the former updates the global counter after accounting. Since we are
    taking the fbc->lock to calculate the precise value of the counter in
    percpu_counter_sum() anyway, it should simply set fbc->count too, as the
    percpu_counter_sum_and_set() does.

    This patch merges these two interfaces into one.

    Signed-off-by: Mingming Cao
    Acked-by: Peter Zijlstra
    Cc:
    Signed-off-by: Andrew Morton
    Signed-off-by: "Theodore Ts'o"

    Mingming Cao
     

12 Jul, 2008

1 commit

  • e8ced39d5   percpu_counter: new function percpu_counter_sum_and_set ... Browse Code »

    Delayed allocation need to check free blocks at every write time.
    percpu_counter_read_positive() is not quit accurate. delayed
    allocation need a more accurate accounting, but using
    percpu_counter_sum_positive() is frequently is quite expensive.

    This patch added a new function to update center counter when sum
    per-cpu counter, to increase the accurate rate for next
    percpu_counter_read() and require less calling expensive
    percpu_counter_sum().

    Signed-off-by: Mingming Cao
    Signed-off-by: "Theodore Ts'o"

    Mingming Cao
     

30 Apr, 2008

1 commit

  • cf0ca9fe5   mm: bdi: export BDI attributes in sysfs ... Browse Code »

    Provide a place in sysfs (/sys/class/bdi) for the backing_dev_info object.
    This allows us to see and set the various BDI specific variables.

    In particular this properly exposes the read-ahead window for all relevant
    users and /sys/block//queue/read_ahead_kb should be deprecated.

    With patient help from Kay Sievers and Greg KH

    [mszeredi@suse.cz]

    - split off NFS and FUSE changes into separate patches
    - document new sysfs attributes under Documentation/ABI
    - do bdi_class_init as a core_initcall, otherwise the "default" BDI
    won't be initialized
    - remove bdi_init_fmt macro, it's not used very much

    [akpm@linux-foundation.org: fix ia64 warning]
    Signed-off-by: Peter Zijlstra
    Cc: Kay Sievers
    Acked-by: Greg KH
    Cc: Trond Myklebust
    Signed-off-by: Miklos Szeredi
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Peter Zijlstra
     

20 Oct, 2007

1 commit

  • d2b20b115   Add irq protection in the percpu-counters cpu-hotplug-callback path ... Browse Code »

    Some of the per-cpu counters and thus their locks are accessed from IRQ
    contexts. This can cause a deadlock if it interrupts a cpu-offline thread
    which is transferring a dead-cpu's counts to the global counter.

    Add appropriate IRQ protection in the cpu-hotplug callback path.

    Signed-off-by: Gautham R Shenoy
    Cc: KAMEZAWA Hiroyuki
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Gautham R Shenoy
     

17 Oct, 2007

8 commits

17 Jul, 2007

2 commits

  • b4ef0296f   percpu_counters: use for_each_online_cpu() ... Browse Code »

    Now that we have implemented hotunplug-time counter spilling,
    percpu_counter_sum() only needs to look at online CPUs.

    Cc: Gautham R Shenoy
    Cc: Oleg Nesterov
    Cc: Peter Zijlstra
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Andrew Morton
     
  • c67ad917c   percpu_counters(): use cpu notifiers ... Browse Code »

    per-cpu counters presently must iterate over all possible CPUs in the
    exhaustive percpu_counter_sum().

    But it can be much better to only iterate over the presently-online CPUs. To
    do this, we must arrange for an offlined CPU's count to be spilled into the
    counter's central count.

    We can do this for all percpu_counters in the machine by linking them into a
    single global list and walking that list at CPU_DEAD time.

    (I hope. Might have race windows in which the percpu_counter_sum() count is
    inaccurate?)

    Cc: Gautham R Shenoy
    Cc: Oleg Nesterov
    Cc: Peter Zijlstra
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Andrew Morton
     

23 Jun, 2006

2 commits

  • 0216bfcff   [PATCH] percpu counter data type changes to suppport more than 2**31 ext3 free blocks counter ... Browse Code »

    The percpu counter data type are changed in this set of patches to support
    more users like ext3 who need more than 32 bit to store the free blocks
    total in the filesystem.

    - Generic perpcu counters data type changes. The size of the global counter
    and local counter were explictly specified using s64 and s32. The global
    counter is changed from long to s64, while the local counter is changed from
    long to s32, so we could avoid doing 64 bit update in most cases.

    - Users of the percpu counters are updated to make use of the new
    percpu_counter_init() routine now taking an additional parameter to allow
    users to pass the initial value of the global counter.

    Signed-off-by: Mingming Cao
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Mingming Cao
     
  • 3cbc56402   [PATCH] percpu_counters: create lib/percpu_counter.c ... Browse Code »

    - Move percpu_counter routines from mm/swap.c to lib/percpu_counter.c

    Signed-off-by: Ravikiran Thirumalai
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Ravikiran G Thirumalai