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=-5.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS 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 50601C433E0 for ; Thu, 28 May 2020 18:20:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 32076207D3 for ; Thu, 28 May 2020 18:20:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="gQ6SZyTu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405743AbgE1SUw (ORCPT ); Thu, 28 May 2020 14:20:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49910 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405733AbgE1SUv (ORCPT ); Thu, 28 May 2020 14:20:51 -0400 Received: from mail-io1-xd42.google.com (mail-io1-xd42.google.com [IPv6:2607:f8b0:4864:20::d42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 74DFCC08C5C6; Thu, 28 May 2020 11:20:50 -0700 (PDT) Received: by mail-io1-xd42.google.com with SMTP id o5so31081045iow.8; Thu, 28 May 2020 11:20:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:reply-to:from:date:message-id :subject:to:cc; bh=G+yj2HNxlB+MWzsxwnefhWDIuMOJPqCPvnYrTA2UP74=; b=gQ6SZyTuCCL92j3EnwabuwoHWaegMI/DNBHghuCxDt1/TMxewtH2VJiIZSBTBtAHmU cch7+RnrPUUpy1GkDPxyAHW0B4wK/hFD95V2MxkzDrRvFzXATbGpJzMk6jWU3gzEdILn QK0IU2GzJtOUIQvG7M7n0iZGqZC8HmsG2OpA/o6a9kzuVARaEuejU2mH9MxfXX5lxOGI NGevO4m2f8soBGDlQM+Unks6RjISfJTHh1KDUp84WZaHJinvLJOj+faLn5jfO9koTYd3 zQRLJbZ1RsyjGfZiYKrOhs67fhJGEeTtUUfCjr3LtgN5LrDSlpUfsmRMtGxomQU4EVO3 FT+Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:reply-to :from:date:message-id:subject:to:cc; bh=G+yj2HNxlB+MWzsxwnefhWDIuMOJPqCPvnYrTA2UP74=; b=K+Z7tu/eVkf7e3xI52A6+6Zps9t6x9cZ808HSz6xyF+bv9Rk/kP7mLAu9HWF6zVuyG dW+WOG4oKz0G0OjbTeLaAKVoXZhhroYjI2Risn3KEMEUvZfG81q2S2gDboBnAZvw5BAA Mkq1nIOQAy/J2ufZPvAUot/8cZcEFQevMcklRm5O+vT0rJbeQs+oAm4eX+B08X7gpY2Z J1lnoMZ25zY2ZbE4RocHoB+xR38ijxrA5NKvugZYndYe8jupmJBS92cZCrpfbWOfdcO1 goS4o9x3hvmlZGgqci4CvNJblvVw64bCc4v22Vr36NniD6fY9NQwq4a9QO800gm1cxmQ Rh/A== X-Gm-Message-State: AOAM532HfyGarl+Jx1tA5zpFAXOLHBWaL28zmGzXU6nClj+3hpU/tn5K YXhhFz8yeiGE0Dc8yrdIMvJIjdQf3Uy3F6+wS6NKb1XMwZg= X-Google-Smtp-Source: ABdhPJytFm8GbsQY0HyRBAyEhNefgJfBXiHUoOeNvKTblmCf3RGMIIVmTCyiLN34onpzEN4yBSv0s5KanGgds8hh0TA= X-Received: by 2002:a02:ca18:: with SMTP id i24mr3767660jak.70.1590690049510; Thu, 28 May 2020 11:20:49 -0700 (PDT) MIME-Version: 1.0 References: <20200526195123.29053-1-axboe@kernel.dk> In-Reply-To: Reply-To: sedat.dilek@gmail.com From: Sedat Dilek Date: Thu, 28 May 2020 20:20:50 +0200 Message-ID: Subject: Re: [PATCHSET v5 0/12] Add support for async buffered reads To: Jens Axboe Cc: io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org Content-Type: text/plain; charset="UTF-8" Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Thu, May 28, 2020 at 7:14 PM Jens Axboe wrote: > > On 5/28/20 11:12 AM, Sedat Dilek wrote: > > On Thu, May 28, 2020 at 7:06 PM Jens Axboe wrote: > >> > >> On 5/28/20 11:02 AM, Sedat Dilek wrote: > >>> On Tue, May 26, 2020 at 10:59 PM Jens Axboe wrote: > >>>> > >>>> We technically support this already through io_uring, but it's > >>>> implemented with a thread backend to support cases where we would > >>>> block. This isn't ideal. > >>>> > >>>> After a few prep patches, the core of this patchset is adding support > >>>> for async callbacks on page unlock. With this primitive, we can simply > >>>> retry the IO operation. With io_uring, this works a lot like poll based > >>>> retry for files that support it. If a page is currently locked and > >>>> needed, -EIOCBQUEUED is returned with a callback armed. The callers > >>>> callback is responsible for restarting the operation. > >>>> > >>>> With this callback primitive, we can add support for > >>>> generic_file_buffered_read(), which is what most file systems end up > >>>> using for buffered reads. XFS/ext4/btrfs/bdev is wired up, but probably > >>>> trivial to add more. > >>>> > >>>> The file flags support for this by setting FMODE_BUF_RASYNC, similar > >>>> to what we do for FMODE_NOWAIT. Open to suggestions here if this is > >>>> the preferred method or not. > >>>> > >>>> In terms of results, I wrote a small test app that randomly reads 4G > >>>> of data in 4K chunks from a file hosted by ext4. The app uses a queue > >>>> depth of 32. If you want to test yourself, you can just use buffered=1 > >>>> with ioengine=io_uring with fio. No application changes are needed to > >>>> use the more optimized buffered async read. > >>>> > >>>> preadv for comparison: > >>>> real 1m13.821s > >>>> user 0m0.558s > >>>> sys 0m11.125s > >>>> CPU ~13% > >>>> > >>>> Mainline: > >>>> real 0m12.054s > >>>> user 0m0.111s > >>>> sys 0m5.659s > >>>> CPU ~32% + ~50% == ~82% > >>>> > >>>> This patchset: > >>>> real 0m9.283s > >>>> user 0m0.147s > >>>> sys 0m4.619s > >>>> CPU ~52% > >>>> > >>>> The CPU numbers are just a rough estimate. For the mainline io_uring > >>>> run, this includes the app itself and all the threads doing IO on its > >>>> behalf (32% for the app, ~1.6% per worker and 32 of them). Context > >>>> switch rate is much smaller with the patchset, since we only have the > >>>> one task performing IO. > >>>> > >>>> Also ran a simple fio based test case, varying the queue depth from 1 > >>>> to 16, doubling every time: > >>>> > >>>> [buf-test] > >>>> filename=/data/file > >>>> direct=0 > >>>> ioengine=io_uring > >>>> norandommap > >>>> rw=randread > >>>> bs=4k > >>>> iodepth=${QD} > >>>> randseed=89 > >>>> runtime=10s > >>>> > >>>> QD/Test Patchset IOPS Mainline IOPS > >>>> 1 9046 8294 > >>>> 2 19.8k 18.9k > >>>> 4 39.2k 28.5k > >>>> 8 64.4k 31.4k > >>>> 16 65.7k 37.8k > >>>> > >>>> Outside of my usual environment, so this is just running on a virtualized > >>>> NVMe device in qemu, using ext4 as the file system. NVMe isn't very > >>>> efficient virtualized, so we run out of steam at ~65K which is why we > >>>> flatline on the patched side (nvme_submit_cmd() eats ~75% of the test app > >>>> CPU). Before that happens, it's a linear increase. Not shown is context > >>>> switch rate, which is massively lower with the new code. The old thread > >>>> offload adds a blocking thread per pending IO, so context rate quickly > >>>> goes through the roof. > >>>> > >>>> The goal here is efficiency. Async thread offload adds latency, and > >>>> it also adds noticable overhead on items such as adding pages to the > >>>> page cache. By allowing proper async buffered read support, we don't > >>>> have X threads hammering on the same inode page cache, we have just > >>>> the single app actually doing IO. > >>>> > >>>> Been beating on this and it's solid for me, and I'm now pretty happy > >>>> with how it all turned out. Not aware of any missing bits/pieces or > >>>> code cleanups that need doing. > >>>> > >>>> Series can also be found here: > >>>> > >>>> https://git.kernel.dk/cgit/linux-block/log/?h=async-buffered.5 > >>>> > >>>> or pull from: > >>>> > >>>> git://git.kernel.dk/linux-block async-buffered.5 > >>>> > >>> > >>> Hi Jens, > >>> > >>> I have pulled linux-block.git#async-buffered.5 on top of Linux v5.7-rc7. > >>> > >>> From first feelings: > >>> The booting into the system (until sddm display-login-manager) took a > >>> bit longer. > >>> The same after login and booting into KDE/Plasma. > >> > >> There is no difference for "regular" use cases, only io_uring with > >> buffered reads will behave differently. So I don't think you have longer > >> boot times due to this. > >> > >>> I am building/linking with LLVM/Clang/LLD v10.0.1-rc1 on Debian/testing AMD64. > >>> > >>> Here I have an internal HDD (SATA) and my Debian-system is on an > >>> external HDD connected via USB-3.0. > >>> Primarily, I use Ext4-FS. > >>> > >>> As said above is the "emotional" side, but I need some technical instructions. > >>> > >>> How can I see Async Buffer Reads is active on a Ext4-FS-formatted partition? > >> > >> You can't see that. It'll always be available on ext4 with this series, > >> and you can watch io_uring instances to see if anyone is using it. > >> > > > > Thanks for answering my questions. > > > > How can I "watch io_uring instances"? > > You can enable io_uring tracing: > > # echo 1 > /sys/kernel/debug/tracing/events/io_uring/io_uring_create/enable > # tail /sys/kernel/debug/tracing/trace > > and see if you get any events for setup. Generally you can also look for > the existence of io_wq_manager processes, these will exist for an > io_uring instance. > > > FIO? > > Debian has fio version 3.19-2 in its apt repositories. > > Version OK? > > Yeah that should work. > I did: # echo 1 > /sys/kernel/debug/tracing/events/io_uring/io_uring_create/enable # cat /sys/kernel/debug/tracing/events/io_uring/io_uring_create/enable 1 # cat ./buf-test-dileks-min [buf-test-dileks-min] filename=/path/to/iso-image-file buffered=1 ioengine=io_uring # fio --showcmd ./buf-test-dileks-min fio --name=buf-test-dileks-min --buffered=1 --ioengine=io_uring --filename=filename=/path/to/iso-image-file # fio ./buf-test-dileks-min # ps -ef | egrep 'f[i]o|i[o]_wq' root 6695 6066 24 20:13 pts/2 00:00:00 fio ./buf-test-dileks-min root 6701 6695 22 20:13 ? 00:00:00 fio ./buf-test-dileks-min root 6702 2 0 20:13 ? 00:00:00 [io_wq_manager] root 6703 2 0 20:13 ? 00:00:00 [io_wqe_worker-0] # LC_ALL=C tail -f /sys/kernel/debug/tracing/trace ... # entries-in-buffer/entries-written: 16/16 #P:4 # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | ... fio-6701 [001] .... 6775.117015: io_uring_create: ring 00000000ef052188, fd 5 sq size 1, cq size 2, flags 0 Looks like this works. Thanks Jens. - Sedat -