From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jun'ichi Nomura" Subject: Re: [PATCH] Fix mapping->writeback_index to point to the last written page Date: Fri, 04 Mar 2011 10:45:30 +0900 Message-ID: <4D70443A.1010602@ce.jp.nec.com> References: <4D676067.8050200@ce.jp.nec.com> <20110302221808.GG7496@quack.suse.cz> <4D6EFC4B.30505@ce.jp.nec.com> <20110303133119.GA16562@localhost> <20110303140802.GA27751@quack.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Wu Fengguang , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" To: Jan Kara Return-path: In-Reply-To: <20110303140802.GA27751@quack.suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 03/03/11 23:08, Jan Kara wrote: > On Thu 03-03-11 21:31:19, Wu Fengguang wrote: >> On Thu, Mar 03, 2011 at 10:26:19AM +0800, Jun'ichi Nomura wrote: >> > flush-8:0-2743 4606: block_bio_queue: 8,0 W 94899962 + 8 >> > flush-8:0-2743 4606: block_bio_queue: 8,0 W 94899970 + 8 >> > flush-8:0-2743 4606: block_bio_queue: 8,0 W 94899978 + 8 >> > flush-8:0-2743 4606: block_bio_queue: 8,0 W 94899986 + 8 >> > flush-8:0-2743 4606: block_bio_queue: 8,0 W 94899994 + 8 >> ==> > kworker/0:1-11 4606: block_rq_issue: 8,0 W 0 () 94899962 + 40 >> > >> flush-8:0-2743 4606: block_bio_queue: 8,0 W 94898554 + 8 >> ==> > >> flush-8:0-2743 4606: block_rq_issue: 8,0 W 0 () 94898554 + 8 >> >> I'd expect the wrapped around 94898554+8 to be merged with 94899962+8. > How could they be merged? They are not continguous... > >> Why kworker/0:1-11 is submitting the request early? And the second >> request is submitted by flush-8:0-2743. > I'm not sure about that either - but I think that kworker is submitting > the work when unplug happens while flush ends up doing it when the queue is > alredy unplugged. Yes. For the above case, it was unplug. For other cases, the reason was max_sectors. Before writeback wraps around, the request has already grown to max_sectors size (~512KB) and doesn't accept new merge. Thanks, -- Jun'ichi Nomura, NEC Corporation