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=-10.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 E3829C4742C for ; Fri, 13 Nov 2020 21:03:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 87D1322252 for ; Fri, 13 Nov 2020 21:03:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="SIqtSJpD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726112AbgKMVDL (ORCPT ); Fri, 13 Nov 2020 16:03:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36694 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725981AbgKMVDK (ORCPT ); Fri, 13 Nov 2020 16:03:10 -0500 Received: from mail-pf1-x444.google.com (mail-pf1-x444.google.com [IPv6:2607:f8b0:4864:20::444]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 580B2C0613D1 for ; Fri, 13 Nov 2020 13:03:09 -0800 (PST) Received: by mail-pf1-x444.google.com with SMTP id q5so8656836pfk.6 for ; Fri, 13 Nov 2020 13:03:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=1zoui9BUZXUZOqrTWaBrZykGcY0FRSZnrRzqMJQ8RwA=; b=SIqtSJpDMUZf6A0Bp680OWghtTzBxCyFEittkvDw3lqzYn2Ps6IVbUdF4Bf3m1dHhb /AsZrlSawXqvZfYZLk1N+1S43FCJPaOfMoqY9qoujbZiA6QWbaEsBAV+otmmbcKGB8uI s3C2sYFRUEPz+dC1Kq9kik/qnrNy+NNJPscbllkTJ7YtOLUIz5k0eVizc3mfmSP+sLta xJd2RATiOoXhTf+2TvePEngYQ7CNZ7PsTd4FUrL8YoF6TkAMthadpjk6+HVaLmvhsqEJ FaPHfuDCO6cHzEUungyCmh3arO6bio30A9vmD/A9kTmX0KS/1Up9Zc2wqdsHsoFMlPk3 NeBw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=1zoui9BUZXUZOqrTWaBrZykGcY0FRSZnrRzqMJQ8RwA=; b=cbBpFSUI/vqEocwM0SGHgcNSW2OOf8Gu1PYsH/6tpWbOYGsJsvY0w0HCm85BjwFYtC WqYLB7dEOyAj+JP3mknR687jUsssI7JiM865iAWJIoLA4GoqErs9Gyy4tcF2kUXqBxW1 SL5YgXbT4F2R310HVhuYOKpPb17JT9Qb5YA/AFngHFuwOme5rIHnOOxWey2y71q+pNbC AiKcJ/bZZijvrP7nsgNdAvE0FA47pE25lndVDtH08lGPHZ1WKpGEd3L3qdiM7FCo3pCx Im42ulWZZhzC1aPC7IbczREWk+lkiafOvKcSg/7PtGnwfTKorM3cO5gakTvFzHN52NBO ip5Q== X-Gm-Message-State: AOAM530Bpqb0W5LhNUJRGkZWFiPqlZganDPqiyO27TC8Yhc9u8vKzHZP gEEZLp4pr28OJmCVHUPusGQ/kNJo2o+6Gw== X-Google-Smtp-Source: ABdhPJy9RxMN3SjWuODbONNveEfQJhguQEGd2j8B+Qx6ue32McdtKQK4nHihEq6cvGxKB+/5V9axzg== X-Received: by 2002:a63:161a:: with SMTP id w26mr3316313pgl.17.1605301388725; Fri, 13 Nov 2020 13:03:08 -0800 (PST) Received: from [192.168.1.134] ([66.219.217.173]) by smtp.gmail.com with ESMTPSA id d2sm11265021pjj.37.2020.11.13.13.03.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 13 Nov 2020 13:03:08 -0800 (PST) Subject: Re: [PATCH] iosched: Add i10 I/O Scheduler To: Sagi Grimberg , Rachit Agarwal , Christoph Hellwig Cc: linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, Keith Busch , Ming Lei , Jaehyun Hwang , Qizhe Cai , Midhul Vuppalapati , Rachit Agarwal , Sagi Grimberg , Rachit Agarwal References: <20201112140752.1554-1-rach4x0r@gmail.com> <5a954c4e-aa84-834d-7d04-0ce3545d45c9@kernel.dk> From: Jens Axboe Message-ID: Date: Fri, 13 Nov 2020 14:03:05 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 11/13/20 1:34 PM, Sagi Grimberg wrote: > >> I haven't taken a close look at the code yet so far, but one quick note >> that patches like this should be against the branches for 5.11. In fact, >> this one doesn't even compile against current -git, as >> blk_mq_bio_list_merge is now called blk_bio_list_merge. > > Ugh, I guess that Jaehyun had this patch bottled up and didn't rebase > before submitting.. Sorry about that. > >> In any case, I did run this through some quick peak testing as I was >> curious, and I'm seeing about 20% drop in peak IOPS over none running >> this. Perf diff: >> >> 10.71% -2.44% [kernel.vmlinux] [k] read_tsc >> 2.33% -1.99% [kernel.vmlinux] [k] _raw_spin_lock > > You ran this with nvme? or null_blk? I guess neither would benefit > from this because if the underlying device will not benefit from > batching (at least enough for the extra cost of accounting for it) it > will be counter productive to use this scheduler. This is nvme, actual device. The initial posting could be a bit more explicit on the use case, it says: "For NVMe SSDs, the i10 I/O scheduler achieves ~60% improvements in terms of IOPS per core over "noop" I/O scheduler." which made me very skeptical, as it sounds like it's raw device claims. Does beg the question of why this is a new scheduler then. It's pretty basic stuff, something that could trivially just be added a side effect of the core (and in fact we have much of it already). Doesn't really seem to warrant a new scheduler at all. There isn't really much in there. >>> [5] https://github.com/i10-kernel/upstream-linux/blob/master/dss-evaluation.pdf >> >> Was curious and wanted to look it up, but it doesn't exist. > > I think this is the right one: > https://github.com/i10-kernel/upstream-linux/blob/master/i10-evaluation.pdf > > We had some back and forth around the naming, hence this was probably > omitted. That works, my local results were a bit worse than listed in there though. And what does this mean: "We note that Linux I/O scheduler introduces an additional kernel worker thread at the I/O dispatching stage" It most certainly does not for the common/hot case. -- Jens Axboe