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=-0.9 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 35004C07E85 for ; Sun, 9 Dec 2018 14:36:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EA8B520837 for ; Sun, 9 Dec 2018 14:36:28 +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="g9vzLfjw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EA8B520837 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-block-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726248AbeLIOg2 (ORCPT ); Sun, 9 Dec 2018 09:36:28 -0500 Received: from mail-pg1-f195.google.com ([209.85.215.195]:44039 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726239AbeLIOg2 (ORCPT ); Sun, 9 Dec 2018 09:36:28 -0500 Received: by mail-pg1-f195.google.com with SMTP id t13so3759442pgr.11 for ; Sun, 09 Dec 2018 06:36:27 -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=HW2INGhN1tc6NzAwcpMbF2PEbFL/bPk7Ndexwvweg0E=; b=g9vzLfjwwxQVL/PAQ0WC0hmHd9CQZ5W1/0HohPVwzQzfTLOzgcspAiOZI/dxm/bxBa nPqQplhgLUEHI7T/rab18fTXIGj8IGxlTDDsP9BGPEPbELJZ1m5ZoL5JDlNhJuzG3YBh pDnRAhC20ukCxflLPb5TqA94ExAfdSNsrF1Spj/ugvp17TFDezCvQWsVKzZYX9NC3uL1 pKDIMszLjeBmXuunc8C5xuzEgnXhamq2R89W6DG5fdiINU1oVXS9c9L/aH2XR44K4uQL bgNysEkuNSvCEjC2t1X+nuLSYPkfvaphm5CfzkiuZMFAQglFUOlTmas+/eCS5TDD3aGD 8eTw== 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=HW2INGhN1tc6NzAwcpMbF2PEbFL/bPk7Ndexwvweg0E=; b=R1Ux36HASAtQLRH/6Hfq96l41bQNrt2AmjaaO/vpUZtlTskQZzk2a0wePam0V/jTa5 Zqmszx/i+F8WLUHKOAr3uVxhTMP3rF9801ZCs2/DRLAIGtrBtkrjRgQw3xWcn+V5iyrS 6R8FllOvrUSssgsNf4+IcPBfdPLkwa8K3Af+HfX/DeLeHr+DoPmigsM6lXlu7+CHMT1J /1vddKFssUL57FlXNECjQHgWGKdu4YdedTTK/YitIvsGaJ2o6O+ESoXmLJ6JqxIPZu3r /tiYRI8VfWFa3LJleFlc0Lx51/ns6fmbScSGdbx6rDIbvxIXBlf9d0LhYxlv1uokbl0R 9vKg== X-Gm-Message-State: AA+aEWZ1odbJmLggEMkhz3HpBhi/ebTbfrVL0btXB5+iDRS8wJta/ioZ 2YoxB7JU59XH/y0oXz++x1KhxQ== X-Google-Smtp-Source: AFSGD/VcgqZG4b/1IhvF9wiTyiyamVOjU9uBOGQCcd0hv/1RvOUw0oUWTUiINd4n7DFp0c+4aLcXjw== X-Received: by 2002:a63:d40a:: with SMTP id a10mr7721303pgh.394.1544366187561; Sun, 09 Dec 2018 06:36:27 -0800 (PST) Received: from [192.168.1.121] (66.29.188.166.static.utbb.net. [66.29.188.166]) by smtp.gmail.com with ESMTPSA id p24sm16864882pfk.155.2018.12.09.06.36.25 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 09 Dec 2018 06:36:26 -0800 (PST) Subject: Re: [PATCH 15/26] aio: support for IO polling To: Benny Halevy , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org Cc: hch@lst.de, jmoyer@redhat.com, clm@fb.com References: <20181207222016.29387-1-axboe@kernel.dk> <20181207222016.29387-16-axboe@kernel.dk> From: Jens Axboe Message-ID: Date: Sun, 9 Dec 2018 07:36:24 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 12/9/18 3:02 AM, Benny Halevy wrote: >> +static int __aio_iopoll_check(struct kioctx *ctx, struct io_event __user *event, >> + unsigned int *nr_events, long min_nr, long max_nr) >> +{ >> + int ret = 0; >> + >> + while (!*nr_events || !need_resched()) { > > Hmm, it doesn't make sense to spin in this loop > if the user got _all_ the events he requested, even > if !need_resched(). How about: > > while (!*nr_events || (!need_resched() && *nr_events < max_nr)) { That checking is done io aio_iopoll_getevents(), there are other conditions where we don't want to spin, like nr_events >= min_nr for instance. But all that logic is in aio_iopoll_getevents(), from here we just know that we probably need to continue if nr_events == 0. I don't think there's an issue here, and no spinning when we don't need it. -- Jens Axboe