From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH v8 1/1] f2fs: dax: implement direct access Date: Wed, 26 Jul 2017 10:20:11 -0700 Message-ID: <20170726172011.GA30142@infradead.org> References: <1500552639-18523-1-git-send-email-sunqiuyang@huawei.com> <20170726072634.GA4684@infradead.org> <20170726170147.GA31930@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" To: Dan Williams Cc: "linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org" , Linux Kernel Mailing List , linux-f2fs-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Christoph Hellwig , linux-fsdevel , Jaegeuk Kim , sunqiuyang List-Id: linux-f2fs-devel.lists.sourceforge.net On Wed, Jul 26, 2017 at 10:11:08AM -0700, Dan Williams wrote: > Until HMAT came along we had no data in the kernel how to pick a sane > default, but we could now very easily make a "if pmem performance < > dram, disable dax by default" policy in the kernel. I'd rather do it the other way around - if HMAT is present and pmem performance >= dram use dax. Else require the explicit -o dax for now to enable it. If an explicit -o nodax is specified disable DAX even if HMAT says it is faster. > The question for this patch is do we want to add yet another > filesystem that adds "-o dax" or require use of per-inode flags to > enable dax. Please stick to the mount option. After spending a lot of time with DAX and various memory techologies I'm pretty confident that the inode flag is the wrong thing to do. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 26 Jul 2017 10:20:11 -0700 From: Christoph Hellwig Subject: Re: [PATCH v8 1/1] f2fs: dax: implement direct access Message-ID: <20170726172011.GA30142@infradead.org> References: <1500552639-18523-1-git-send-email-sunqiuyang@huawei.com> <20170726072634.GA4684@infradead.org> <20170726170147.GA31930@infradead.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Dan Williams Cc: "linux-nvdimm@lists.01.org" , Linux Kernel Mailing List , linux-f2fs-devel@lists.sourceforge.net, Christoph Hellwig , linux-fsdevel , Jaegeuk Kim , sunqiuyang List-ID: On Wed, Jul 26, 2017 at 10:11:08AM -0700, Dan Williams wrote: > Until HMAT came along we had no data in the kernel how to pick a sane > default, but we could now very easily make a "if pmem performance < > dram, disable dax by default" policy in the kernel. I'd rather do it the other way around - if HMAT is present and pmem performance >= dram use dax. Else require the explicit -o dax for now to enable it. If an explicit -o nodax is specified disable DAX even if HMAT says it is faster. > The question for this patch is do we want to add yet another > filesystem that adds "-o dax" or require use of per-inode flags to > enable dax. Please stick to the mount option. After spending a lot of time with DAX and various memory techologies I'm pretty confident that the inode flag is the wrong thing to do. _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org ([65.50.211.133]:60869 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751202AbdGZRUL (ORCPT ); Wed, 26 Jul 2017 13:20:11 -0400 Date: Wed, 26 Jul 2017 10:20:11 -0700 From: Christoph Hellwig To: Dan Williams Cc: Christoph Hellwig , "linux-nvdimm@lists.01.org" , Linux Kernel Mailing List , linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel , Jaegeuk Kim , sunqiuyang Subject: Re: [PATCH v8 1/1] f2fs: dax: implement direct access Message-ID: <20170726172011.GA30142@infradead.org> References: <1500552639-18523-1-git-send-email-sunqiuyang@huawei.com> <20170726072634.GA4684@infradead.org> <20170726170147.GA31930@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed, Jul 26, 2017 at 10:11:08AM -0700, Dan Williams wrote: > Until HMAT came along we had no data in the kernel how to pick a sane > default, but we could now very easily make a "if pmem performance < > dram, disable dax by default" policy in the kernel. I'd rather do it the other way around - if HMAT is present and pmem performance >= dram use dax. Else require the explicit -o dax for now to enable it. If an explicit -o nodax is specified disable DAX even if HMAT says it is faster. > The question for this patch is do we want to add yet another > filesystem that adds "-o dax" or require use of per-inode flags to > enable dax. Please stick to the mount option. After spending a lot of time with DAX and various memory techologies I'm pretty confident that the inode flag is the wrong thing to do.