From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx189.postini.com [74.125.245.189]) by kanga.kvack.org (Postfix) with SMTP id C01456B005C for ; Sun, 10 Jun 2012 00:54:25 -0400 (EDT) Received: by pbbrp2 with SMTP id rp2so5089243pbb.14 for ; Sat, 09 Jun 2012 21:54:25 -0700 (PDT) Date: Sun, 10 Jun 2012 12:54:03 +0800 From: Wanpeng Li Subject: Re: [PATCH] page-writeback.c: fix update bandwidth time judgment error Message-ID: <20120610045300.GA29336@kernel> Reply-To: Wanpeng Li References: <1339302005-366-1-git-send-email-liwp.linux@gmail.com> <20120610043641.GA10355@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120610043641.GA10355@localhost> Sender: owner-linux-mm@kvack.org List-ID: To: Fengguang Wu Cc: LKML , Jan Kara , Andrew Morton , PeterZijlstra , Johannes Weiner , linux-mm@kvack.org, Gavin Shan , Wanpeng Li On Sun, Jun 10, 2012 at 12:36:41PM +0800, Fengguang Wu wrote: >Wanpeng, > >Sorry this I won't take this: it don't really improve anything. Even >with the changed test, the real intervals are still some random values >above (and not far away from) 200ms.. We are saying about 200ms >intervals just for convenience. > But some parts like: __bdi_update_bandwidth which bdi_update_bandwidth will call: if(elapsed < BANDWIDTH_INTERVAL) return; or global_update_bandwidth: if(time_before(now, update_time + BANDWIDTH_INTERVAL)) return; You me just ignore this disunion ? Regards, Wanpeng Li > >On Sun, Jun 10, 2012 at 12:20:05PM +0800, Wanpeng Li wrote: >> From: Wanpneg Li >> >> Since bdi_update_bandwidth function should estimate write bandwidth at 200ms intervals, >> so the time is bdi->bw_time_stamp + BANDWIDTH_INTERVAL == jiffies, but >> if use time_is_after_eq_jiffies intervals will be bdi->bw_time_stamp + >> BANDWIDTH_INTERVAL + 1. >> >> Signed-off-by: Wanpeng Li >> --- >> mm/page-writeback.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/page-writeback.c b/mm/page-writeback.c >> index c833bf0..099e225 100644 >> --- a/mm/page-writeback.c >> +++ b/mm/page-writeback.c >> @@ -1032,7 +1032,7 @@ static void bdi_update_bandwidth(struct backing_dev_info *bdi, >> unsigned long bdi_dirty, >> unsigned long start_time) >> { >> - if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL)) >> + if (time_is_after_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL)) >> return; >> spin_lock(&bdi->wb.list_lock); >> __bdi_update_bandwidth(bdi, thresh, bg_thresh, dirty, >> -- >> 1.7.9.5 -- 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/ . Don't email: email@kvack.org