* [PATCH 1/2]block cfq: don't use atomic_t for cfq_queue
@ 2010-12-23 2:45 Shaohua Li
2010-12-23 15:05 ` Jeff Moyer
2010-12-23 15:16 ` Vivek Goyal
0 siblings, 2 replies; 3+ messages in thread
From: Shaohua Li @ 2010-12-23 2:45 UTC (permalink / raw)
To: lkml; +Cc: Jens Axboe, vgoyal, jmoyer
cfq_queue->ref is used with queue_lock hold, so ref doesn't need to be an atomic
and atomic operation is slower.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
---
block/cfq-iosched.c | 27 ++++++++++++++++-----------
1 file changed, 16 insertions(+), 11 deletions(-)
Index: linux/block/cfq-iosched.c
===================================================================
--- linux.orig/block/cfq-iosched.c 2010-12-22 21:14:15.000000000 +0800
+++ linux/block/cfq-iosched.c 2010-12-23 10:44:23.000000000 +0800
@@ -97,7 +97,7 @@ struct cfq_rb_root {
*/
struct cfq_queue {
/* reference count */
- atomic_t ref;
+ int ref;
/* various state flags, see below */
unsigned int flags;
/* parent cfq_data */
@@ -2040,7 +2040,7 @@ static int cfqq_process_refs(struct cfq_
int process_refs, io_refs;
io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
- process_refs = atomic_read(&cfqq->ref) - io_refs;
+ process_refs = cfqq->ref - io_refs;
BUG_ON(process_refs < 0);
return process_refs;
}
@@ -2080,10 +2080,10 @@ static void cfq_setup_merge(struct cfq_q
*/
if (new_process_refs >= process_refs) {
cfqq->new_cfqq = new_cfqq;
- atomic_add(process_refs, &new_cfqq->ref);
+ new_cfqq->ref += process_refs;
} else {
new_cfqq->new_cfqq = cfqq;
- atomic_add(new_process_refs, &cfqq->ref);
+ cfqq->ref += new_process_refs;
}
}
@@ -2538,9 +2538,10 @@ static void cfq_put_queue(struct cfq_que
struct cfq_data *cfqd = cfqq->cfqd;
struct cfq_group *cfqg, *orig_cfqg;
- BUG_ON(atomic_read(&cfqq->ref) <= 0);
+ BUG_ON(cfqq->ref <= 0);
- if (!atomic_dec_and_test(&cfqq->ref))
+ cfqq->ref--;
+ if (cfqq->ref)
return;
cfq_log_cfqq(cfqd, cfqq, "put_queue");
@@ -2843,7 +2844,7 @@ static void cfq_init_cfqq(struct cfq_dat
RB_CLEAR_NODE(&cfqq->p_node);
INIT_LIST_HEAD(&cfqq->fifo);
- atomic_set(&cfqq->ref, 0);
+ cfqq->ref = 0;
cfqq->cfqd = cfqd;
cfq_mark_cfqq_prio_changed(cfqq);
@@ -2979,11 +2980,11 @@ cfq_get_queue(struct cfq_data *cfqd, boo
* pin the queue now that it's allocated, scheduler exit will prune it
*/
if (!is_sync && !(*async_cfqq)) {
- atomic_inc(&cfqq->ref);
+ cfqq->ref++;
*async_cfqq = cfqq;
}
- atomic_inc(&cfqq->ref);
+ cfqq->ref++;
return cfqq;
}
@@ -3681,7 +3682,7 @@ new_queue:
}
cfqq->allocated[rw]++;
- atomic_inc(&cfqq->ref);
+ cfqq->ref++;
spin_unlock_irqrestore(q->queue_lock, flags);
@@ -3862,6 +3863,10 @@ static void *cfq_init_queue(struct reque
if (!cfqd)
return NULL;
+ /*
+ * Don't need take queue_lock in the routine, since we are
+ * initializing the ioscheduler, and nobody is using cfqd
+ */
cfqd->cic_index = i;
/* Init root service tree */
@@ -3901,7 +3906,7 @@ static void *cfq_init_queue(struct reque
* will not attempt to free it.
*/
cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
- atomic_inc(&cfqd->oom_cfqq.ref);
+ cfqd->oom_cfqq.ref++;
cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
INIT_LIST_HEAD(&cfqd->cic_list);
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 1/2]block cfq: don't use atomic_t for cfq_queue
2010-12-23 2:45 [PATCH 1/2]block cfq: don't use atomic_t for cfq_queue Shaohua Li
@ 2010-12-23 15:05 ` Jeff Moyer
2010-12-23 15:16 ` Vivek Goyal
1 sibling, 0 replies; 3+ messages in thread
From: Jeff Moyer @ 2010-12-23 15:05 UTC (permalink / raw)
To: Shaohua Li; +Cc: lkml, Jens Axboe, vgoyal
Shaohua Li <shaohua.li@intel.com> writes:
> cfq_queue->ref is used with queue_lock hold, so ref doesn't need to be an atomic
> and atomic operation is slower.
>
> Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 1/2]block cfq: don't use atomic_t for cfq_queue
2010-12-23 2:45 [PATCH 1/2]block cfq: don't use atomic_t for cfq_queue Shaohua Li
2010-12-23 15:05 ` Jeff Moyer
@ 2010-12-23 15:16 ` Vivek Goyal
1 sibling, 0 replies; 3+ messages in thread
From: Vivek Goyal @ 2010-12-23 15:16 UTC (permalink / raw)
To: Shaohua Li; +Cc: lkml, Jens Axboe, jmoyer
On Thu, Dec 23, 2010 at 10:45:33AM +0800, Shaohua Li wrote:
> cfq_queue->ref is used with queue_lock hold, so ref doesn't need to be an atomic
> and atomic operation is slower.
>
> Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Looks good to me.
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Vivek
>
> ---
> block/cfq-iosched.c | 27 ++++++++++++++++-----------
> 1 file changed, 16 insertions(+), 11 deletions(-)
>
> Index: linux/block/cfq-iosched.c
> ===================================================================
> --- linux.orig/block/cfq-iosched.c 2010-12-22 21:14:15.000000000 +0800
> +++ linux/block/cfq-iosched.c 2010-12-23 10:44:23.000000000 +0800
> @@ -97,7 +97,7 @@ struct cfq_rb_root {
> */
> struct cfq_queue {
> /* reference count */
> - atomic_t ref;
> + int ref;
> /* various state flags, see below */
> unsigned int flags;
> /* parent cfq_data */
> @@ -2040,7 +2040,7 @@ static int cfqq_process_refs(struct cfq_
> int process_refs, io_refs;
>
> io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
> - process_refs = atomic_read(&cfqq->ref) - io_refs;
> + process_refs = cfqq->ref - io_refs;
> BUG_ON(process_refs < 0);
> return process_refs;
> }
> @@ -2080,10 +2080,10 @@ static void cfq_setup_merge(struct cfq_q
> */
> if (new_process_refs >= process_refs) {
> cfqq->new_cfqq = new_cfqq;
> - atomic_add(process_refs, &new_cfqq->ref);
> + new_cfqq->ref += process_refs;
> } else {
> new_cfqq->new_cfqq = cfqq;
> - atomic_add(new_process_refs, &cfqq->ref);
> + cfqq->ref += new_process_refs;
> }
> }
>
> @@ -2538,9 +2538,10 @@ static void cfq_put_queue(struct cfq_que
> struct cfq_data *cfqd = cfqq->cfqd;
> struct cfq_group *cfqg, *orig_cfqg;
>
> - BUG_ON(atomic_read(&cfqq->ref) <= 0);
> + BUG_ON(cfqq->ref <= 0);
>
> - if (!atomic_dec_and_test(&cfqq->ref))
> + cfqq->ref--;
> + if (cfqq->ref)
> return;
>
> cfq_log_cfqq(cfqd, cfqq, "put_queue");
> @@ -2843,7 +2844,7 @@ static void cfq_init_cfqq(struct cfq_dat
> RB_CLEAR_NODE(&cfqq->p_node);
> INIT_LIST_HEAD(&cfqq->fifo);
>
> - atomic_set(&cfqq->ref, 0);
> + cfqq->ref = 0;
> cfqq->cfqd = cfqd;
>
> cfq_mark_cfqq_prio_changed(cfqq);
> @@ -2979,11 +2980,11 @@ cfq_get_queue(struct cfq_data *cfqd, boo
> * pin the queue now that it's allocated, scheduler exit will prune it
> */
> if (!is_sync && !(*async_cfqq)) {
> - atomic_inc(&cfqq->ref);
> + cfqq->ref++;
> *async_cfqq = cfqq;
> }
>
> - atomic_inc(&cfqq->ref);
> + cfqq->ref++;
> return cfqq;
> }
>
> @@ -3681,7 +3682,7 @@ new_queue:
> }
>
> cfqq->allocated[rw]++;
> - atomic_inc(&cfqq->ref);
> + cfqq->ref++;
>
> spin_unlock_irqrestore(q->queue_lock, flags);
>
> @@ -3862,6 +3863,10 @@ static void *cfq_init_queue(struct reque
> if (!cfqd)
> return NULL;
>
> + /*
> + * Don't need take queue_lock in the routine, since we are
> + * initializing the ioscheduler, and nobody is using cfqd
> + */
> cfqd->cic_index = i;
>
> /* Init root service tree */
> @@ -3901,7 +3906,7 @@ static void *cfq_init_queue(struct reque
> * will not attempt to free it.
> */
> cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
> - atomic_inc(&cfqd->oom_cfqq.ref);
> + cfqd->oom_cfqq.ref++;
> cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
>
> INIT_LIST_HEAD(&cfqd->cic_list);
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2010-12-23 15:16 UTC | newest]
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2010-12-23 2:45 [PATCH 1/2]block cfq: don't use atomic_t for cfq_queue Shaohua Li
2010-12-23 15:05 ` Jeff Moyer
2010-12-23 15:16 ` Vivek Goyal
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