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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 26C70C433EF for ; Thu, 21 Apr 2022 12:32:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1384802AbiDUMfH (ORCPT ); Thu, 21 Apr 2022 08:35:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41236 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1384790AbiDUMfH (ORCPT ); Thu, 21 Apr 2022 08:35:07 -0400 Received: from mail-ej1-x62a.google.com (mail-ej1-x62a.google.com [IPv6:2a00:1450:4864:20::62a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F01AE3191C for ; Thu, 21 Apr 2022 05:32:11 -0700 (PDT) Received: by mail-ej1-x62a.google.com with SMTP id y10so9687475ejw.8 for ; Thu, 21 Apr 2022 05:32:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Lh828Yrhk3RT/O9ogfgnIki+uJ9VN1M1Mm/MjWXiRpE=; b=hyhnUTRbWLmvo4mUKjHN65JwSm75vRdjPWbg7TTB/zUXX7lZeSUWcjkDiNJM4ZBTKF nYWcoGZuZnkH6JPEYPVL2eOoTBJi+BPFNKoIlyKobRb7D8L2/N0GboJa0rxxp9ynAooU pK/PzywgGf4w3nMjULLUb9BIkIDZOTTv/bSp0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Lh828Yrhk3RT/O9ogfgnIki+uJ9VN1M1Mm/MjWXiRpE=; b=PqF0WJndzCaGd0KxjDcueY3HvVcL66bRpJqc9ll4/hhSvrLCLyja5BGeKYaY8TcmSQ vSRkilDgUDvsLLFbkNto0IruiCB22QlrOagZnYBi4+HP73eaOVt72gknfhRljHPArcwc kfUDvW5jIGsToRqxiQutE4Eh6QJdWGHTZTvjg38WlgdRHW9g0RnOh8BGLwPjdXXbXtre rL/qQbWPl/YjKWg2LizzrJ811IGufQVd0Fhh7v7E9b5NiWzRHA2LnjJ6WoAAnzCp3byY d+RuIi9l1RLNVgmqTvaG6W2CIJWCDyxlIpNxqvC5kvjV9Ry3y+YmICBK5X7KnFLfMqlA smQg== X-Gm-Message-State: AOAM5308K5ZdDPuL3U/ud8QAXF10imZS0gG1pd8F/XYy7HK1TWtKyjDY SS0b59i417HqYDL/izEavyM/ZugoGbJHsOyQo+GMGA== X-Google-Smtp-Source: ABdhPJwE9jULwzbY0bPzBMu0ZWWz4sAucpNZ/OP8Cu58bY7syvSuie0c4Gn4osXVSqZnpR8CR3kvjVGloBq41NN2MJc= X-Received: by 2002:a17:906:280b:b0:6ce:f3c7:688f with SMTP id r11-20020a170906280b00b006cef3c7688fmr22645761ejc.468.1650544330461; Thu, 21 Apr 2022 05:32:10 -0700 (PDT) MIME-Version: 1.0 References: <23b62cca-8ec5-f250-e5a3-7e9ed983e190@kernel.dk> <77229971-72cd-7d78-d790-3ef4789acc9e@kernel.dk> <61c2336f-0315-5f76-3022-18c80f79e0b5@kernel.dk> <38436a44-5048-2062-c339-66679ae1e282@kernel.dk> <47912c4c-ccc2-0678-6c2f-3e3c0dd1f04b@kernel.dk> In-Reply-To: From: Miklos Szeredi Date: Thu, 21 Apr 2022 14:31:58 +0200 Message-ID: Subject: Re: io_uring_prep_openat_direct() and link/drain To: Jens Axboe Cc: io-uring@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Tue, 5 Apr 2022 at 16:44, Jens Axboe wrote: > > On 4/5/22 1:45 AM, Miklos Szeredi wrote: > > On Sat, 2 Apr 2022 at 03:17, Jens Axboe wrote: > >> > >> On 4/1/22 10:21 AM, Jens Axboe wrote: > >>> On 4/1/22 10:02 AM, Miklos Szeredi wrote: > >>>> On Fri, 1 Apr 2022 at 17:36, Jens Axboe wrote: > >>>> > >>>>> I take it you're continually reusing those slots? > >>>> > >>>> Yes. > >>>> > >>>>> If you have a test > >>>>> case that'd be ideal. Agree that it sounds like we just need an > >>>>> appropriate breather to allow fput/task_work to run. Or it could be the > >>>>> deferral free of the fixed slot. > >>>> > >>>> Adding a breather could make the worst case latency be large. I think > >>>> doing the fput synchronously would be better in general. > >>> > >>> fput() isn't sync, it'll just offload to task_work. There are some > >>> dependencies there that would need to be checked. But we'll find a way > >>> to deal with it. > >>> > >>>> I test this on an VM with 8G of memory and run the following: > >>>> > >>>> ./forkbomb 14 & > >>>> # wait till 16k processes are forked > >>>> for i in `seq 1 100`; do ./procreads u; done > >>>> > >>>> You can compare performance with plain reads (./procreads p), the > >>>> other tests don't work on public kernels. > >>> > >>> OK, I'll check up on this, but probably won't have time to do so before > >>> early next week. > >> > >> Can you try with this patch? It's not complete yet, there's actually a > >> bunch of things we can do to improve the direct descriptor case. But > >> this one is easy enough to pull off, and I think it'll fix your OOM > >> case. Not a proposed patch, but it'll prove the theory. > > > > Sorry for the delay.. > > > > Patch works like charm. > > OK good, then it is the issue I suspected. Thanks for testing! Tested with v5.18-rc3 and performance seems significantly worse than with the test patch: test patch: avg min max stdev real 0.205 0.190 0.266 0.011 user 0.017 0.007 0.029 0.004 sys 0.374 0.336 0.503 0.022 5.18.0-rc3-00016-gb253435746d9: avg min max stdev real 0.725 0.200 18.090 2.279 user 0.019 0.005 0.046 0.006 sys 0.454 0.241 1.022 0.199 Thanks, Miklos