Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755882AbbDUTFv (ORCPT ); Tue, 21 Apr 2015 15:05:51 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:60927 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753817AbbDUTFt (ORCPT ); Tue, 21 Apr 2015 15:05:49 -0400 Message-ID: <55369F7A.7090108@fb.com> Date: Tue, 21 Apr 2015 13:05:30 -0600 From: Jens Axboe User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Ming Lin CC: Ming Lin , lkml , , Dave Chinner , Changho Choi-SSI , "Kwan (Hingkwan) Huen-SSI" Subject: Re: [RFC DRAFT PATCH] per-buffered-write stream IDs References: <1429636187-30236-1-git-send-email-ming.l@samsung.com> <55368512.1020503@fb.com> In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [192.168.52.13] X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.13.68,1.0.33,0.0.0000 definitions=2015-04-21_06:2015-04-21,2015-04-21,1970-01-01 signatures=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1976 Lines: 53 On 04/21/2015 12:34 PM, Ming Lin wrote: > On Tue, Apr 21, 2015 at 10:12 AM, Jens Axboe wrote: >> On 04/21/2015 11:09 AM, Ming Lin wrote: >>> >>> Hi Jens, >>> >>> This RFC DRAFT patch is on top of your "[PATCH v2] Support for write >>> stream IDs" >>> I throw it out early to get comments if it's the way to go. >>> >>> Quote LWN(http://lwn.net/Articles/638722): >>> >>> "There would be clear value in a closer association between stream IDs >>> and specific buffered-write operations. Getting there would require >>> storing >>> the stream ID with each dirtied page, though; that, in turn, almost >>> certainly >>> implies shoehorning the stream ID into the associated page structure. >>> That would not be an easy task; it is not surprising that it is not a part >>> of >>> this patch set. Should the lack of per-buffered-write stream IDs prove to >>> be >>> a serious constraint in the future, somebody will certainly be motivated >>> to >>> try to find a place to store another eight bits in struct page." >>> >>> This draft patch stores stream_id in buffer head instead of page. >> >> >> This is pointless. You need to store it in the page, if the whole point is >> that you want this to be trackable. And adding it to struct page would be a >> no-go, we can't increase the size of that. See various other discussions >> around, for instance, IO priorities for buffered writeback and tracking that >> state on the side. > > I googled, but didn't find related discussions. > Could you please point me a link? This is the most recent effort: https://lwn.net/Articles/628631/ My point is that adding it to the buffer_head accomplishes nothing. You need to track from when the page was dirtied. -- Jens Axboe -- 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/