]> git.baikalelectronics.ru Git - kernel.git/commit
percpu_counter: batch size aware __percpu_counter_compare()
authorDave Chinner <dchinner@redhat.com>
Thu, 28 May 2015 21:39:34 +0000 (07:39 +1000)
committerDave Chinner <david@fromorbit.com>
Thu, 28 May 2015 21:39:34 +0000 (07:39 +1000)
commit78452ec54864b35177eddbca43ee978526ae57a5
treeba795195e42d33c4fc8436a1c80d954a1057ab7f
parentadae9aa268d1401ca03962e01c74e98dba8ea807
percpu_counter: batch size aware __percpu_counter_compare()

XFS uses non-stanard batch sizes for avoiding frequent global
counter updates on it's allocated inode counters, as they increment
or decrement in batches of 64 inodes. Hence the standard percpu
counter batch of 32 means that the counter is effectively a global
counter. Currently Xfs uses a batch size of 128 so that it doesn't
take the global lock on every single modification.

However, Xfs also needs to compare accurately against zero, which
means we need to use percpu_counter_compare(), and that has a
hard-coded batch size of 32, and hence will spuriously fail to
detect when it is supposed to use precise comparisons and hence
the accounting goes wrong.

Add __percpu_counter_compare() to take a custom batch size so we can
use it sanely in XFS and factor percpu_counter_compare() to use it.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
include/linux/percpu_counter.h
lib/percpu_counter.c