Messages in this thread Patch in this message | | | Date | Mon, 30 Oct 2006 23:48:43 +0300 | From | Oleg Nesterov <> | Subject | [PATCH] taskstats_exit_alloc: optimize/simplify |
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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>
--- STATS/kernel/taskstats.c~1_alloc 2006-10-29 18:35:40.000000000 +0300 +++ STATS/kernel/taskstats.c 2006-10-30 23:45:20.000000000 +0300 @@ -421,7 +421,6 @@ 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 @@ -429,19 +428,11 @@ void taskstats_exit_alloc(struct tasksta */ *mycpu = raw_smp_processor_id(); - *ptidstats = NULL; - tmp = kmem_cache_zalloc(taskstats_cache, SLAB_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, SLAB_KERNEL); } /* Send pid data out on exit */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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