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[PATCH] taskstats_exit_alloc: optimize/simplify 

If there are no listeners, every task does unneeded kmem_cache alloc/free on
exit. We don't need listeners->sem for 'if (!list_empty())' check. Yes, we may
have a false positive, but this doesn't differ from the case when the listener
is unregistered after we drop the semaphore. So we don't need to do allocation
beforehand.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Balbir Singh <balbir@in.ibm.com>
Acked-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Oleg Nesterov 2006-12-06 20:36:50 -08:00 committed by Linus Torvalds
parent 38da288b8b
commit 128fb95650
1 changed files with 4 additions and 13 deletions
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17
kernel/taskstats.c
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@ -416,7 +416,6 @@ err:
void taskstats_exit_alloc(struct taskstats **ptidstats, unsigned int *mycpu)
{
struct listener_list *listeners;
struct taskstats *tmp;
/*
* This is the cpu on which the task is exiting currently and will
* be the one for which the exit event is sent, even if the cpu
@ -424,19 +423,11 @@ void taskstats_exit_alloc(struct taskstats **ptidstats, unsigned int *mycpu)
*/
*mycpu = raw_smp_processor_id();
*ptidstats = NULL;
tmp = kmem_cache_zalloc(taskstats_cache, GFP_KERNEL);
if (!tmp)
return;
listeners = &per_cpu(listener_array, *mycpu);
down_read(&listeners->sem);
if (!list_empty(&listeners->list)) {
*ptidstats = tmp;
tmp = NULL;
}
up_read(&listeners->sem);
kfree(tmp);
*ptidstats = NULL;
if (!list_empty(&listeners->list))
*ptidstats = kmem_cache_zalloc(taskstats_cache, GFP_KERNEL);
}
/* Send pid data out on exit */