From 0b6b098efcddac2bf4e2a895c9b655560bbfcee4 Mon Sep 17 00:00:00 2001 From: Mathias Krause Date: Fri, 25 Oct 2013 12:14:15 +0200 Subject: 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 Acked-by: Steffen Klassert Signed-off-by: Herbert Xu --- include/linux/padata.h | 3 +-- kernel/padata.c | 9 ++++----- 2 files changed, 5 insertions(+), 7 deletions(-) diff --git a/include/linux/padata.h b/include/linux/padata.h index 86292beebfe2..438694650471 100644 --- a/include/linux/padata.h +++ b/include/linux/padata.h @@ -129,10 +129,9 @@ struct parallel_data { struct padata_serial_queue __percpu *squeue; atomic_t reorder_objects; atomic_t refcnt; + atomic_t seq_nr; struct padata_cpumask cpumask; spinlock_t lock ____cacheline_aligned; - spinlock_t seq_lock; - unsigned int seq_nr; unsigned int processed; struct timer_list timer; }; 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; -- cgit v1.2.3-59-g8ed1b