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=-5.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 CB34EC433E2 for ; Mon, 20 Jul 2020 16:39:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AA88322D0B for ; Mon, 20 Jul 2020 16:39:39 +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="WGiBVFDx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730061AbgGTQjf (ORCPT ); Mon, 20 Jul 2020 12:39:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40390 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730966AbgGTPtF (ORCPT ); Mon, 20 Jul 2020 11:49:05 -0400 Received: from mail-il1-x142.google.com (mail-il1-x142.google.com [IPv6:2607:f8b0:4864:20::142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BFD51C061794 for ; Mon, 20 Jul 2020 08:49:04 -0700 (PDT) Received: by mail-il1-x142.google.com with SMTP id a11so13734980ilk.0 for ; Mon, 20 Jul 2020 08:49:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=D/CA+/3/bTndVqHDVfOkxSHtDGUPSGt5x3VVKQfqZbg=; b=WGiBVFDxkDK9ZFg0IrwsBU9TGmD+ri9d6HGdShiF1Ll+N1iHXGFQmIfLUSjif3Cmp+ AVeUuZqUIux5ykvvGzRtLUa1DylQFhVVOKR7da7PHAgVzIKkJcHa7BONkoYjb/tCizfw 1j4ywtzIffpQMa6dfjP3vGDCMKE5fn+PykRLQgbP431T/6VxhaOEmuCQyGkis6crNs5T HmAg41n3TmKIBU5R3qZ0YW8M+/EMEkE+3TpK2YDfQrsc5H8hJC9ES3ygxd+39EonR6Cx BDO3PHM1BrFlmkKI/BU0weuKzZ9PE3fTQTc4HoMAoDdTfYmVdfAxVSUf4Jd14SZHpD+K LVhg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=D/CA+/3/bTndVqHDVfOkxSHtDGUPSGt5x3VVKQfqZbg=; b=WpdW48cVyB5mVE3bXxGyg/kXGkDwOBmP//6ESikjpGxh3x8ylRqkcTXv347S4di4SL YQ7iBldMJojrwIinSgmSAIzlRbzAcblzGpZ2+ybQV2V9dB/KJNfPw738MEAub3EbOFLD LymWYlk7eKzSp/wCZ34PqzPlbkysu+AFqX/tae7xM6CdMt6lu4xOdgAwoCji0G1MGYI9 PQNdSCA4HQBeXQoi/UuQVKMEiap+VMM1ayQH4oVQcjIXtG15bQWtX1ecsr7B2Tr8nnd0 z1M0KEP7wAwmDYyGhLIvLOTEFEN9h7NFv+F6qFwaWcMNDxhnSeFARqay9ZlpZWCmIbIt QQWQ== X-Gm-Message-State: AOAM532oELvRRqjA04u/tkmw4r9oYjslxCKar4mK/sF+2aYpe2gV1vzy M+HEGqXhpT5AnJOxempYnoVR6Q== X-Google-Smtp-Source: ABdhPJxoefCUr9kZLZrdpjB1/kG/khSkCyqABdVEAysM2MGxbfvjcaNVbWEaW6P3bgONfYG5iyq/kw== X-Received: by 2002:a05:6e02:605:: with SMTP id t5mr23516270ils.116.1595260144075; Mon, 20 Jul 2020 08:49:04 -0700 (PDT) Received: from [192.168.1.58] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id z78sm9474809ilk.72.2020.07.20.08.49.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Jul 2020 08:49:03 -0700 (PDT) Subject: Re: [PATCH 0/2] task_put batching To: Pavel Begunkov , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: From: Jens Axboe Message-ID: Date: Mon, 20 Jul 2020 09:49:02 -0600 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 Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 7/20/20 9:22 AM, Pavel Begunkov wrote: > On 18/07/2020 17:37, Jens Axboe wrote: >> On 7/18/20 2:32 AM, Pavel Begunkov wrote: >>> For my a bit exaggerated test case perf continues to show high CPU >>> cosumption by io_dismantle(), and so calling it io_iopoll_complete(). >>> Even though the patch doesn't yield throughput increase for my setup, >>> probably because the effect is hidden behind polling, but it definitely >>> improves relative percentage. And the difference should only grow with >>> increasing number of CPUs. Another reason to have this is that atomics >>> may affect other parallel tasks (e.g. which doesn't use io_uring) >>> >>> before: >>> io_iopoll_complete: 5.29% >>> io_dismantle_req: 2.16% >>> >>> after: >>> io_iopoll_complete: 3.39% >>> io_dismantle_req: 0.465% >> >> Still not seeing a win here, but it's clean and it _should_ work. For >> some reason I end up getting the offset in task ref put growing the >> fput_many(). Which doesn't (on the surface) make a lot of sense, but >> may just mean that we have some weird side effects. > > It grows because the patch is garbage, the second condition is always false. > See the diff. Could you please drop both patches? Hah, indeed. With this on top, it looks like it should in terms of performance and profiles. I can just fold this into the existing one, if you'd like. -- Jens Axboe