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_PASS,USER_AGENT_MUTT autolearn=unavailable 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 EE9C8C4151A for ; Tue, 29 Jan 2019 10:07:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C7F2B20881 for ; Tue, 29 Jan 2019 10:07:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727513AbfA2KHF (ORCPT ); Tue, 29 Jan 2019 05:07:05 -0500 Received: from mx2.suse.de ([195.135.220.15]:36094 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725799AbfA2KHE (ORCPT ); Tue, 29 Jan 2019 05:07:04 -0500 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 51B5DB01F; Tue, 29 Jan 2019 10:07:03 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 47B8F1E3FEA; Tue, 29 Jan 2019 11:07:02 +0100 (CET) Date: Tue, 29 Jan 2019 11:07:02 +0100 From: Jan Kara To: Keith Busch Cc: Jan Kara , Kanchan Joshi , "linux-fsdevel@vger.kernel.org" , "linux-block@vger.kernel.org" , "linux-ext4@vger.kernel.org" , "linux-nvme@lists.infradead.org" , "jack@suse.com" , "david@fromorbit.com" , "tytso@mit.edu" , "prakash.v@samsung.com" , Jens Axboe Subject: Re: [PATCH v2 0/4] Write-hint for FS journal Message-ID: <20190129100702.GA29981@quack2.suse.cz> References: <1547047861-7271-1-git-send-email-joshi.k@samsung.com> <20190125162353.GA11210@localhost.localdomain> <20190128124709.GB27972@quack2.suse.cz> <20190128232423.GD15302@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190128232423.GD15302@localhost.localdomain> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Mon 28-01-19 16:24:24, Keith Busch wrote: > On Mon, Jan 28, 2019 at 04:47:09AM -0800, Jan Kara wrote: > > On Fri 25-01-19 09:23:53, Keith Busch wrote: > > > On Wed, Jan 09, 2019 at 09:00:57PM +0530, Kanchan Joshi wrote: > > > > Towards supporing write-hints/streams for filesystem journal. > > > > > > > > Here is the v1 patch for background - > > > > https://marc.info/?l=linux-fsdevel&m=154444637519020&w=2 > > > > > > > > Changes since v1: > > > > - introduce four more hints for in-kernel use, as recommended by Dave chinner > > > > & Jens axboe. This isolates kernel-mode hints from user-mode ones. > > > > > > The nvme driver disables streams if the controller doesn't support > > > BLK_MAX_WRITE_HINT number of streams, so this series breaks the feature > > > for controllers that only support up to 4. > > > > Right. Do you know if there are such controllers? Or are you just afraid > > that there could be? > > I've asked around, and the concensus I received is all currently support > at least 8, but they couldn't say if that would be true for potential > lower budget products. Can we implement a reasonable fallback to use > what's available? OK, thanks for input. So probably we should just map kernel stream IDs to 0 if the device doesn't support them. But that probably means we need to propagate number of available streams up from NVME into the block layer so that this can be handled reasonably seamlessly. Jens, Kanchan? Honza -- Jan Kara SUSE Labs, CR