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-rw-r--r--fs/xfs/support/ktrace.c22
-rw-r--r--fs/xfs/support/ktrace.h1
2 files changed, 15 insertions, 8 deletions
diff --git a/fs/xfs/support/ktrace.c b/fs/xfs/support/ktrace.c
index 4e0444c0aca6..0b75d302508f 100644
--- a/fs/xfs/support/ktrace.c
+++ b/fs/xfs/support/ktrace.c
@@ -24,7 +24,7 @@ static int ktrace_zentries;
void __init
ktrace_init(int zentries)
{
- ktrace_zentries = zentries;
+ ktrace_zentries = roundup_pow_of_two(zentries);
ktrace_hdr_zone = kmem_zone_init(sizeof(ktrace_t),
"ktrace_hdr");
@@ -47,13 +47,16 @@ ktrace_uninit(void)
* ktrace_alloc()
*
* Allocate a ktrace header and enough buffering for the given
- * number of entries.
+ * number of entries. Round the number of entries up to a
+ * power of 2 so we can do fast masking to get the index from
+ * the atomic index counter.
*/
ktrace_t *
ktrace_alloc(int nentries, unsigned int __nocast sleep)
{
ktrace_t *ktp;
ktrace_entry_t *ktep;
+ int entries;
ktp = (ktrace_t*)kmem_zone_alloc(ktrace_hdr_zone, sleep);
@@ -70,11 +73,12 @@ ktrace_alloc(int nentries, unsigned int __nocast sleep)
/*
* Special treatment for buffers with the ktrace_zentries entries
*/
- if (nentries == ktrace_zentries) {
+ entries = roundup_pow_of_two(nentries);
+ if (entries == ktrace_zentries) {
ktep = (ktrace_entry_t*)kmem_zone_zalloc(ktrace_ent_zone,
sleep);
} else {
- ktep = (ktrace_entry_t*)kmem_zalloc((nentries * sizeof(*ktep)),
+ ktep = (ktrace_entry_t*)kmem_zalloc((entries * sizeof(*ktep)),
sleep | KM_LARGE);
}
@@ -91,7 +95,9 @@ ktrace_alloc(int nentries, unsigned int __nocast sleep)
}
ktp->kt_entries = ktep;
- ktp->kt_nentries = nentries;
+ ktp->kt_nentries = entries;
+ ASSERT(is_power_of_2(entries));
+ ktp->kt_index_mask = entries - 1;
atomic_set(&ktp->kt_index, 0);
ktp->kt_rollover = 0;
return ktp;
@@ -160,7 +166,7 @@ ktrace_enter(
* Grab an entry by pushing the index up to the next one.
*/
index = atomic_add_return(1, &ktp->kt_index);
- index = (index - 1) % ktp->kt_nentries;
+ index = (index - 1) & ktp->kt_index_mask;
if (!ktp->kt_rollover && index == ktp->kt_nentries - 1)
ktp->kt_rollover = 1;
@@ -197,7 +203,7 @@ ktrace_nentries(
if (ktp == NULL)
return 0;
- index = atomic_read(&ktp->kt_index) % ktp->kt_nentries;
+ index = atomic_read(&ktp->kt_index) & ktp->kt_index_mask;
return (ktp->kt_rollover ? ktp->kt_nentries : index);
}
@@ -223,7 +229,7 @@ ktrace_first(ktrace_t *ktp, ktrace_snap_t *ktsp)
int nentries;
if (ktp->kt_rollover)
- index = atomic_read(&ktp->kt_index) % ktp->kt_nentries;
+ index = atomic_read(&ktp->kt_index) & ktp->kt_index_mask;
else
index = 0;
diff --git a/fs/xfs/support/ktrace.h b/fs/xfs/support/ktrace.h
index 782dbbb6a9d0..741d6947ca60 100644
--- a/fs/xfs/support/ktrace.h
+++ b/fs/xfs/support/ktrace.h
@@ -31,6 +31,7 @@ typedef struct ktrace_entry {
typedef struct ktrace {
int kt_nentries; /* number of entries in trace buf */
atomic_t kt_index; /* current index in entries */
+ unsigned int kt_index_mask;
int kt_rollover;
ktrace_entry_t *kt_entries; /* buffer of entries */
} ktrace_t;
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