From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f69.google.com (mail-pg0-f69.google.com [74.125.83.69]) by kanga.kvack.org (Postfix) with ESMTP id 9FA1A6B0292 for ; Thu, 10 Aug 2017 00:00:17 -0400 (EDT) Received: by mail-pg0-f69.google.com with SMTP id 123so84616196pga.5 for ; Wed, 09 Aug 2017 21:00:17 -0700 (PDT) Received: from lgeamrelo11.lge.com (LGEAMRELO11.lge.com. [156.147.23.51]) by mx.google.com with ESMTP id q3si3882566plk.256.2017.08.09.21.00.15 for ; Wed, 09 Aug 2017 21:00:16 -0700 (PDT) Date: Thu, 10 Aug 2017 13:00:14 +0900 From: Minchan Kim Subject: Re: [PATCH v1 2/6] fs: use on-stack-bio if backing device has BDI_CAP_SYNC capability Message-ID: <20170810040014.GA2042@bbox> References: <1502175024-28338-1-git-send-email-minchan@kernel.org> <1502175024-28338-3-git-send-email-minchan@kernel.org> <20170808124959.GB31390@bombadil.infradead.org> <20170808132904.GC31390@bombadil.infradead.org> <20170809015113.GB32338@bbox> <20170809023122.GF31390@bombadil.infradead.org> <20170809024150.GA32471@bbox> <20170810030433.GG31390@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170810030433.GG31390@bombadil.infradead.org> Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ross Zwisler , "karam . lee" , seungho1.park@lge.com, Christoph Hellwig , Dan Williams , Dave Chinner , jack@suse.cz, Jens Axboe , Vishal Verma , linux-nvdimm@lists.01.org, kernel-team On Wed, Aug 09, 2017 at 08:04:33PM -0700, Matthew Wilcox wrote: > On Wed, Aug 09, 2017 at 11:41:50AM +0900, Minchan Kim wrote: > > On Tue, Aug 08, 2017 at 07:31:22PM -0700, Matthew Wilcox wrote: > > > On Wed, Aug 09, 2017 at 10:51:13AM +0900, Minchan Kim wrote: > > > > On Tue, Aug 08, 2017 at 06:29:04AM -0700, Matthew Wilcox wrote: > > > > > On Tue, Aug 08, 2017 at 05:49:59AM -0700, Matthew Wilcox wrote: > > > > > > + struct bio sbio; > > > > > > + struct bio_vec sbvec; > > > > > > > > > > ... this needs to be sbvec[nr_pages], of course. > > > > > > > > > > > - bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), > > > > > > + if (bdi_cap_synchronous_io(inode_to_bdi(inode))) { > > > > > > + bio = &sbio; > > > > > > + bio_init(bio, &sbvec, nr_pages); > > > > > > > > > > ... and this needs to be 'sbvec', not '&sbvec'. > > > > > > > > I don't get it why we need sbvec[nr_pages]. > > > > On-stack-bio works with per-page. > > > > May I miss something? > > > > > > The way I redid it, it will work with an arbitrary number of pages. > > > > IIUC, it would be good things with dynamic bio alloction with passing > > allocated bio back and forth but on-stack bio cannot work like that. > > It should be done in per-page so it is worth? > > I'm not passing the bio back and forth between do_mpage_readpage() and > its callers. The version I sent allows for multiple pages in a single > on-stack bio (when called from mpage_readpages()). I'm confused. I want to confirm your thought before respinning. Please correct me if I miss something. The version you sent to me used on-stack bio within do_mpage_readpage so that's why I said sbvec[nr_pages] would be pointless because it works with per-page base unless if we use dynamic bio allocation. But I guess now you suggest to use on-stack bio in mpage_readpages so single on-stack bio in mpage_readpages's stack can batch multiple pages in bvecs of a bio. Right? -- 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