tree aea65e2a9f1f6ca5c3f8dd44b78c5a9dd5adaee3
parent 44d814ced4cffbfe6a775c5bb8b941a6e734e7d9
author David Chinner <dgc@sgi.com> 1204771535 +1100
committer Lachlan McIlroy <lachlan@redback.melbourne.sgi.com> 1208482795 +1000

[XFS] Use atomic counters for ktrace buffer indexes

ktrace_enter() is consuming vast amounts of CPU time due to the use of a
single global lock for protecting buffer index increments. Change it to
use per-buffer atomic counters - this reduces ktrace_enter() overhead
during a trace intensive test on a 4p machine from 58% of all CPU time to
12% and halves test runtime.

SGI-PV: 977546
SGI-Modid: xfs-linux-melb:xfs-kern:30537a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>