From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A0F31C18E7D for ; Wed, 22 May 2019 10:25:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 69D6820868 for ; Wed, 22 May 2019 10:25:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728827AbfEVKZd (ORCPT ); Wed, 22 May 2019 06:25:33 -0400 Received: from mx2.suse.de ([195.135.220.15]:60474 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727464AbfEVKZc (ORCPT ); Wed, 22 May 2019 06:25:32 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 35A53AEB6; Wed, 22 May 2019 10:25:31 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 804F91E3C5F; Wed, 22 May 2019 12:25:30 +0200 (CEST) Date: Wed, 22 May 2019 12:25:30 +0200 From: Jan Kara To: 'Christoph Hellwig' Cc: Jan Kara , kanchan , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, prakash.v@samsung.com, anshul@samsung.com, "Martin K. Petersen" Subject: Re: [PATCH v5 0/7] Extend write-hint framework, and add write-hint for Ext4 journal Message-ID: <20190522102530.GK17019@quack2.suse.cz> References: <1556191202-3245-1-git-send-email-joshi.k@samsung.com> <20190510170249.GA26907@infradead.org> <00fb01d50c71$dd358e50$97a0aaf0$@samsung.com> <20190520142719.GA15705@infradead.org> <20190521082528.GA17709@quack2.suse.cz> <20190521082846.GA11024@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190521082846.GA11024@infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue 21-05-19 01:28:46, 'Christoph Hellwig' wrote: > On Tue, May 21, 2019 at 10:25:28AM +0200, Jan Kara wrote: > > performance benefits for some drives. After all you can just think about it > > like RWH_WRITE_LIFE_JOURNAL type of hint available for the kernel... > > Except that it actuallys adds a parallel insfrastructure. A > RWH_WRITE_LIFE_JOURNAL would be much more palatable, but someone needs > to explain how that is: > > a) different from RWH_WRITE_LIFE_SHORT The problem I have with this is: What does "short" mean? What if userspace's notion of short differs from the kernel notion? Also the journal block lifetime is somewhat hard to predict. It depends on the size of the journal and metadata load on the filesystem so there's big variance. So all we really know is that all journal blocks are the same. > b) would not apply to a log/journal maintained in userspace that works > exactly the same Lifetime of userspace journal/log may be significantly different from the lifetime of the filesystem journal. So using the same hint for them does not look like a great idea? Honza -- Jan Kara SUSE Labs, CR