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 C6265C433EF for ; Thu, 21 Apr 2022 12:34:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1382268AbiDUMg6 (ORCPT ); Thu, 21 Apr 2022 08:36:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42010 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1377192AbiDUMg4 (ORCPT ); Thu, 21 Apr 2022 08:36:56 -0400 Received: from mail-pg1-x529.google.com (mail-pg1-x529.google.com [IPv6:2607:f8b0:4864:20::529]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1B4A520BE3 for ; Thu, 21 Apr 2022 05:34:06 -0700 (PDT) Received: by mail-pg1-x529.google.com with SMTP id k14so4569773pga.0 for ; Thu, 21 Apr 2022 05:34:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20210112.gappssmtp.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:content-language:to :cc:references:from:in-reply-to:content-transfer-encoding; bh=nq91BNyZp1XIprDKEGxcW+lLng2cM9BD77qb5uQR8j0=; b=g3mjVtScLnEKzmgZWHlLNvSBJtQla85ScprZ/NyEXYypgBEzudW1xHeJ2lvQVjovhS t58E8rlUVQatiyIPgoZ9YSMG/VruKAgOAa6e5fDkm1BkVkGYn20+m1iXHxsKt92/7K4+ RvgGxjc0uFVd3u7YWZQp6EWASOu0RUT3/mwSchoyGOkPgx7H9haWwgeyrVYQl/IffuRJ U6VuK6serKi5oeGrlYxciosQoPRDHIClylsX3CFOSrvEy1QLOnYjIqSOpryHPvKzgbgC gmwXxnqMMPN+Aw+pKWd74w3MceblheEanmMMeKAdEZAyODTdkKm4ds7VirXJB9Z2wDgR 5JaQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=nq91BNyZp1XIprDKEGxcW+lLng2cM9BD77qb5uQR8j0=; b=Aj8HFIhfHRKskT0DZyiP4B4s2K7iBjxhZ6h9jmbR22WLO2JPVsLtujdRtk7uE/5wnj qCIWKbZJYks3wncy9HJihfxbWoszg51Ro6sCL0dlNZEQaNUYOt/Ko79RBrtDx5uIVlYk 5ofwsZ6Gtot56KvfKszvzykg1oI4oKXs4lwD+B4ITmjGTZEo13Nh8MgfJzHoZYgOEtqZ VtVlZ+mVXFGUbpfiR628MLMQ8/CGfKrOUwFOBNTzHmmolaC+Us0aCeCYK88Zc6LUHPx+ NqdT64OiDC2A3z6xMOpBXGLK8KTvOpmzEzeBh5Ys/25Y+r8c2dcD4mCD0yWgXLZNjCkz KN2Q== X-Gm-Message-State: AOAM533j/l5+RgnPg7S5L/UynIxfVOlqCwGahtpeJTLRM3X9mrK1fcI1 IuKHdeJvjhk6cAksqMyobSt3GbGSSzDCZF8o X-Google-Smtp-Source: ABdhPJy5dB8dr7uT/wR0codm8XEnemUUcUM8e+jDWXtiI///z7hZ4b56uM5GLDC4hw0sTSFdhDpS0g== X-Received: by 2002:a63:cf4d:0:b0:399:40fc:addf with SMTP id b13-20020a63cf4d000000b0039940fcaddfmr23611399pgj.416.1650544445477; Thu, 21 Apr 2022 05:34:05 -0700 (PDT) Received: from [192.168.1.100] ([198.8.77.157]) by smtp.gmail.com with ESMTPSA id y21-20020a631815000000b0039fcedd7bedsm24060377pgl.41.2022.04.21.05.34.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 21 Apr 2022 05:34:04 -0700 (PDT) Message-ID: <05c068ed-4af1-f12e-623f-6a9dde73d1c0@kernel.dk> Date: Thu, 21 Apr 2022 06:34:03 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: io_uring_prep_openat_direct() and link/drain Content-Language: en-US To: Miklos Szeredi Cc: io-uring@vger.kernel.org References: <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> From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 4/21/22 6:31 AM, Miklos Szeredi wrote: > 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 It's been a month and I don't remember details of which patches were tested, when you say "test patch", which one exactly are you referring to and what base was it applied on? -- Jens Axboe