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authorMathias Krause <mathias.krause@secunet.com>2013-10-25 12:14:15 +0200
committerHerbert Xu <herbert@gondor.apana.org.au>2013-10-30 12:02:58 +0800
commit0b6b098efcddac2bf4e2a895c9b655560bbfcee4 (patch)
tree0facc6f31504a5be471d4592f99bce0b28f995e2 /kernel/padata.c
parentcfc6f11b768a9bdda17aac280474de1f0e344fea (diff)
downloadlinux-0b6b098efcddac2bf4e2a895c9b655560bbfcee4.tar.bz2
padata: make the sequence counter an atomic_t
Using a spinlock to atomically increase a counter sounds wrong -- we've atomic_t for this! Also move 'seq_nr' to a different cache line than 'lock' to reduce cache line trashing. This has the nice side effect of decreasing the size of struct parallel_data from 192 to 128 bytes for a x86-64 build, e.g. occupying only two instead of three cache lines. Those changes results in a 5% performance increase on an IPsec test run using pcrypt. Btw. the seq_lock spinlock was never explicitly initialized -- one more reason to get rid of it. Signed-off-by: Mathias Krause <mathias.krause@secunet.com> Acked-by: Steffen Klassert <steffen.klassert@secunet.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'kernel/padata.c')
-rw-r--r--kernel/padata.c9
1 files changed, 4 insertions, 5 deletions
diff --git a/kernel/padata.c b/kernel/padata.c
index 07af2c95dcfe..2abd25d79cc8 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -46,6 +46,7 @@ static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index)
static int padata_cpu_hash(struct parallel_data *pd)
{
+ unsigned int seq_nr;
int cpu_index;
/*
@@ -53,10 +54,8 @@ static int padata_cpu_hash(struct parallel_data *pd)
* seq_nr mod. number of cpus in use.
*/
- spin_lock(&pd->seq_lock);
- cpu_index = pd->seq_nr % cpumask_weight(pd->cpumask.pcpu);
- pd->seq_nr++;
- spin_unlock(&pd->seq_lock);
+ seq_nr = atomic_inc_return(&pd->seq_nr);
+ cpu_index = seq_nr % cpumask_weight(pd->cpumask.pcpu);
return padata_index_to_cpu(pd, cpu_index);
}
@@ -429,7 +428,7 @@ static struct parallel_data *padata_alloc_pd(struct padata_instance *pinst,
padata_init_pqueues(pd);
padata_init_squeues(pd);
setup_timer(&pd->timer, padata_reorder_timer, (unsigned long)pd);
- pd->seq_nr = 0;
+ atomic_set(&pd->seq_nr, -1);
atomic_set(&pd->reorder_objects, 0);
atomic_set(&pd->refcnt, 0);
pd->pinst = pinst;