Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751743AbdGaHRJ (ORCPT ); Mon, 31 Jul 2017 03:17:09 -0400 Received: from verein.lst.de ([213.95.11.211]:56166 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750923AbdGaHRI (ORCPT ); Mon, 31 Jul 2017 03:17:08 -0400 Date: Mon, 31 Jul 2017 09:17:07 +0200 From: Christoph Hellwig To: Minchan Kim Cc: Andrew Morton , Matthew Wilcox , Ross Zwisler , linux-kernel@vger.kernel.org, "karam . lee" , Jerome Marchand , Nitin Gupta , seungho1.park@lge.com, Christoph Hellwig , Dan Williams , Dave Chinner , Jan Kara , Jens Axboe , Vishal Verma , linux-nvdimm@lists.01.org Subject: Re: [PATCH 0/3] remove rw_page() from brd, pmem and btt Message-ID: <20170731071707.GA16299@lst.de> References: <20170728165604.10455-1-ross.zwisler@linux.intel.com> <20170728173143.GE15980@bombadil.infradead.org> <20170728142123.729b20e9fcf45c6a814f18e7@linux-foundation.org> <20170730221659.GA28031@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170730221659.GA28031@bbox> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 406 Lines: 8 On Mon, Jul 31, 2017 at 07:16:59AM +0900, Minchan Kim wrote: > rw_page's gain is reducing of dynamic allocation in swap path > as well as performance gain thorugh avoiding bio allocation. > And it would be important in memory pressure situation. There is no need for any dynamic allocation when using the bio path. Take a look at __blkdev_direct_IO_simple for an example that doesn't do any allocations.