From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:44008 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727048AbeKEVVe (ORCPT ); Mon, 5 Nov 2018 16:21:34 -0500 Date: Mon, 5 Nov 2018 20:01:54 +0800 From: Ming Lei To: Johannes Thumshirn Cc: Jens Axboe , Linux Block Layer Mailinglist , Hannes Reinecke , Linux Kernel Mailinglist , Jan Kara , Sagi Grimberg Subject: Re: [PATCH] block: respect virtual boundary mask in bvecs Message-ID: <20181105120153.GD12367@ming.t460p> References: <20181105102301.9752-1-jthumshirn@suse.de> <20181105105548.GC12367@ming.t460p> <7c649b43-f952-cf94-93d6-44fb153acced@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <7c649b43-f952-cf94-93d6-44fb153acced@suse.de> Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org On Mon, Nov 05, 2018 at 12:50:50PM +0100, Johannes Thumshirn wrote: > On 05/11/2018 11:55, Ming Lei wrote: > > On Mon, Nov 05, 2018 at 11:23:01AM +0100, Johannes Thumshirn wrote: > >> With drivers like iSer we are seeing a lot of bio splitting and smaller I/Os > >> being submitted to the driver. > >> > >> The root cause of this issue that the virtual boundary mask code does not take > >> into consideration that some of the memory segments in the SG list may have > >> come from a huge memory page that is being managed in the SG list as 4K > > > > I guess you mean something like 64K PAGE_SIZE, instead of huge page. > > No I mean like a 2M page from an upper layer. If you mean the real huge page, this patch shouldn't have made a difference because bio_vec->bv_offset is in [0, PAGE_SIZE), and iSer sets virt boundary as 4K - 1. However, things will change after multipage bvec is introduced. Thanks, Ming