From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 2A755900163 for ; Mon, 1 Aug 2011 20:35:10 -0400 (EDT) Received: from m3.gw.fujitsu.co.jp (unknown [10.0.50.73]) by fgwmail6.fujitsu.co.jp (Postfix) with ESMTP id 872E83EE0BB for ; Tue, 2 Aug 2011 09:35:07 +0900 (JST) Received: from smail (m3 [127.0.0.1]) by outgoing.m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 685EE45DEB3 for ; Tue, 2 Aug 2011 09:35:07 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (s3.gw.fujitsu.co.jp [10.0.50.93]) by m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 42BD445DE9E for ; Tue, 2 Aug 2011 09:35:07 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id 30C411DB8041 for ; Tue, 2 Aug 2011 09:35:07 +0900 (JST) Received: from m105.s.css.fujitsu.com (m105.s.css.fujitsu.com [10.240.81.145]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id DEE7F1DB8038 for ; Tue, 2 Aug 2011 09:35:06 +0900 (JST) Message-ID: <4E374637.20202@jp.fujitsu.com> Date: Tue, 02 Aug 2011 09:35:03 +0900 From: KOSAKI Motohiro MIME-Version: 1.0 Subject: Re: [patch 3/3]vmscan: cleanup kswapd_try_to_sleep References: <1311840789.15392.409.camel@sli10-conroe> In-Reply-To: <1311840789.15392.409.camel@sli10-conroe> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: shaohua.li@intel.com Cc: akpm@linux-foundation.org, linux-mm@kvack.org, mgorman@suse.de, minchan.kim@gmail.com (2011/07/28 17:13), Shaohua Li wrote: > cleanup kswapd_try_to_sleep() a little bit. Sometimes kswapd doesn't > really sleep. In such case, don't call prepare_to_wait/finish_wait. > It just wastes CPU. > > Signed-off-by: Shaohua Li > --- > mm/vmscan.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > Index: linux/mm/vmscan.c > =================================================================== > --- linux.orig/mm/vmscan.c 2011-07-28 15:52:35.000000000 +0800 > +++ linux/mm/vmscan.c 2011-07-28 15:55:56.000000000 +0800 > @@ -2709,13 +2709,11 @@ static void kswapd_try_to_sleep(pg_data_ > if (freezing(current) || kthread_should_stop()) > return; > > - prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); > - > /* Try to sleep for a short interval */ > if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { > + prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); > remaining = schedule_timeout(HZ/10); > finish_wait(&pgdat->kswapd_wait, &wait); > - prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); > } > > /* > @@ -2734,7 +2732,9 @@ static void kswapd_try_to_sleep(pg_data_ > * them before going back to sleep. > */ > set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); > + prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); > schedule(); > + finish_wait(&pgdat->kswapd_wait, &wait); > set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); > } else { > if (remaining) > @@ -2742,7 +2742,6 @@ static void kswapd_try_to_sleep(pg_data_ > else > count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); > } > - finish_wait(&pgdat->kswapd_wait, &wait); > } > > /* Prepare_to_wait/finish_wait basic usage is below. Briefly, 1) prepare_to_wait() is needed to call every sleeping 2) finish_wait is only need to exit sleeping loop So, 1) moving prepare_to_wait looks pretty good to me. but I doubt the worth of moving the finish_wait of function last. ------------------------------------------------------------------------- #define __wait_event(wq, condition) \ do { \ DEFINE_WAIT(__wait); \ \ for (;;) { \ prepare_to_wait(&wq, &__wait, TASK_UNINTERRUPTIBLE); \ if (condition) \ break; \ schedule(); \ } \ finish_wait(&wq, &__wait); \ } while (0) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org