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| author | David Chinner <dgc@sgi.com> | 2008-03-06 13:45:35 +1100 |
|---|---|---|
| committer | Lachlan McIlroy <lachlan@redback.melbourne.sgi.com> | 2008-04-18 11:39:55 +1000 |
| commit | 6ee4752ffe782be6e86bea1403a2fe0f682aa71a (patch) | |
| tree | aea65e2a9f1f6ca5c3f8dd44b78c5a9dd5adaee3 /fs/xfs/support | |
| parent | 44d814ced4cffbfe6a775c5bb8b941a6e734e7d9 (diff) | |
| download | linux-6ee4752ffe782be6e86bea1403a2fe0f682aa71a.tar.gz | |
[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>
Diffstat (limited to 'fs/xfs/support')
| -rw-r--r-- | fs/xfs/support/ktrace.c | 21 | ||||
| -rw-r--r-- | fs/xfs/support/ktrace.h | 2 |
2 files changed, 9 insertions, 14 deletions
diff --git a/fs/xfs/support/ktrace.c b/fs/xfs/support/ktrace.c index 129067cfcb86..4e0444c0aca6 100644 --- a/fs/xfs/support/ktrace.c +++ b/fs/xfs/support/ktrace.c @@ -92,7 +92,7 @@ ktrace_alloc(int nentries, unsigned int __nocast sleep) ktp->kt_entries = ktep; ktp->kt_nentries = nentries; - ktp->kt_index = 0; + atomic_set(&ktp->kt_index, 0); ktp->kt_rollover = 0; return ktp; } @@ -151,8 +151,6 @@ ktrace_enter( void *val14, void *val15) { - static DEFINE_SPINLOCK(wrap_lock); - unsigned long flags; int index; ktrace_entry_t *ktep; @@ -161,12 +159,8 @@ ktrace_enter( /* * Grab an entry by pushing the index up to the next one. */ - spin_lock_irqsave(&wrap_lock, flags); - index = ktp->kt_index; - if (++ktp->kt_index == ktp->kt_nentries) - ktp->kt_index = 0; - spin_unlock_irqrestore(&wrap_lock, flags); - + index = atomic_add_return(1, &ktp->kt_index); + index = (index - 1) % ktp->kt_nentries; if (!ktp->kt_rollover && index == ktp->kt_nentries - 1) ktp->kt_rollover = 1; @@ -199,11 +193,12 @@ int ktrace_nentries( ktrace_t *ktp) { - if (ktp == NULL) { + int index; + if (ktp == NULL) return 0; - } - return (ktp->kt_rollover ? ktp->kt_nentries : ktp->kt_index); + index = atomic_read(&ktp->kt_index) % ktp->kt_nentries; + return (ktp->kt_rollover ? ktp->kt_nentries : index); } /* @@ -228,7 +223,7 @@ ktrace_first(ktrace_t *ktp, ktrace_snap_t *ktsp) int nentries; if (ktp->kt_rollover) - index = ktp->kt_index; + index = atomic_read(&ktp->kt_index) % ktp->kt_nentries; else index = 0; diff --git a/fs/xfs/support/ktrace.h b/fs/xfs/support/ktrace.h index 56e72b40a859..782dbbb6a9d0 100644 --- a/fs/xfs/support/ktrace.h +++ b/fs/xfs/support/ktrace.h @@ -30,7 +30,7 @@ typedef struct ktrace_entry { */ typedef struct ktrace { int kt_nentries; /* number of entries in trace buf */ - int kt_index; /* current index in entries */ + atomic_t kt_index; /* current index in entries */ int kt_rollover; ktrace_entry_t *kt_entries; /* buffer of entries */ } ktrace_t; |