Messages in this thread | | | Date | Mon, 30 Oct 2006 22:04:47 -0500 | From | Shailabh Nagar <> | Subject | Re: [PATCH] taskstats_exit_alloc: optimize/simplify |
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Oleg Nesterov wrote: > 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.
Sounds reasonable.
> > Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Shailabh Nagar <nagar@watson.ibm.com>
> > --- 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 */ >
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