Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752246AbbEZPfS (ORCPT ); Tue, 26 May 2015 11:35:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56374 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750726AbbEZPfP (ORCPT ); Tue, 26 May 2015 11:35:15 -0400 Date: Tue, 26 May 2015 16:34:14 +0100 From: Alasdair G Kergon To: Ming Lin Cc: Mike Snitzer , lkml , Christoph Hellwig , Kent Overstreet , Jens Axboe , Dongsu Park , Christoph Hellwig , Al Viro , Ming Lei , Neil Brown , Alasdair Kergon , dm-devel@redhat.com, Lars Ellenberg , drbd-user@lists.linbit.com, Jiri Kosina , Geoff Levand , Jim Paris , Joshua Morris , Philip Kelleher , Minchan Kim , Nitin Gupta , Oleg Drokin , Andreas Dilger , Dave Chinner Subject: Re: [PATCH v4 01/11] block: make generic_make_request handle arbitrarily sized bios Message-ID: <20150526153414.GA31182@agk-dp.fab.redhat.com> Mail-Followup-To: Ming Lin , Mike Snitzer , lkml , Christoph Hellwig , Kent Overstreet , Jens Axboe , Dongsu Park , Christoph Hellwig , Al Viro , Ming Lei , Neil Brown , Alasdair Kergon , dm-devel@redhat.com, Lars Ellenberg , drbd-user@lists.linbit.com, Jiri Kosina , Geoff Levand , Jim Paris , Joshua Morris , Philip Kelleher , Minchan Kim , Nitin Gupta , Oleg Drokin , Andreas Dilger , Dave Chinner References: <1432318723-18829-1-git-send-email-mlin@kernel.org> <1432318723-18829-2-git-send-email-mlin@kernel.org> <20150526143626.GA4315@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Red Hat UK Ltd. Registered in England and Wales, number 03798903. Registered Office: 64 Baker Street, 4th floor, London, W1U 7DF. User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 720 Lines: 17 On Tue, May 26, 2015 at 08:02:08AM -0700, Ming Lin wrote: > Now bio_add_page() can build lager bios. > And blk_queue_split() can split the bios in ->make_request() if needed. But why not try to make the bio the right size in the first place so you don't have to incur the performance impact of splitting? What performance testing have you yet done to demonstrate the *actual* impact of this patchset in situations where merge_bvec_fn is currently a net benefit? Alasdair -- 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/