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 2E052C65BAF for ; Mon, 10 Dec 2018 08:10:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E909C20855 for ; Mon, 10 Dec 2018 08:10:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=scylladb-com.20150623.gappssmtp.com header.i=@scylladb-com.20150623.gappssmtp.com header.b="aGFBg6jj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E909C20855 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=scylladb.com 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 S1726050AbeLJIKq (ORCPT ); Mon, 10 Dec 2018 03:10:46 -0500 Received: from mail-wm1-f67.google.com ([209.85.128.67]:54910 "EHLO mail-wm1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726236AbeLJIKq (ORCPT ); Mon, 10 Dec 2018 03:10:46 -0500 Received: by mail-wm1-f67.google.com with SMTP id a62so2447842wmh.4 for ; Mon, 10 Dec 2018 00:10:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=scylladb-com.20150623.gappssmtp.com; s=20150623; h=message-id:subject:from:to:cc:date:in-reply-to:references :user-agent:mime-version:content-transfer-encoding; bh=sjkW69AJsjNm9vM+hyYZea61s4UL+vXEnJM9jpCEopw=; b=aGFBg6jj2+k5H6gKvJUaTJYPYrWRnzaouEynMksQECt+IEHJfzEOejStT4xCFCztRe +GsZs1YALWJkaBREYSq0MgvmEy/Qq3LpX2LnZnLskd79FivmfTwbSHdC9VtMoAYkUJwW U0aG9sf+HIwG8+GS+AGjOKpiFETtK27QgiKF1zOautPvpaIj/bVI+fRPxMetsmryQO50 MsbtuXYJi477payIkCVR87MPYmgdHHDJSantTSELjlnlqiKZI6FuYJShY7FXGLkZPEbO YoLTSnNttYpqQhVWt4BLLAQ8dK/J3q8RDAdabDcUs3QTktqL2B5sdEEVDKkRM9C1pkI2 rMnA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:user-agent:mime-version:content-transfer-encoding; bh=sjkW69AJsjNm9vM+hyYZea61s4UL+vXEnJM9jpCEopw=; b=Fr+A7N7KFQDca1tV1EpYz624JZXtERGqc0NAHSHfzWWpJwgvkbEwOD/mKz6IhHr1wl 8jbbshkNnd8poCM2JfxtgYBsLsPBjQ2JcSG69TX+nHmjvNW08owEzeWn7SHxuaTKZj2F MEd/rhV6BWUg6FZ8ajKR2J33kOAU2cfN+lmxBYyUVHNg+2vYjCKhEvdEMUQ/IrPPrYPE TpKw6mK7NYmm+xA6DXcRVN17StK5CtLWzaU0AHnIhYEE5dQeDFrIe3YLMoo+OoTR9xvv vf4CsvR/V1JYRYqd8LtBgCqZN4TQRvcl9ti9Ox4qg8qaWsqGWprDtw1i/l5xYWqBQBza e4ew== X-Gm-Message-State: AA+aEWa4EYVqDLLTg+SCGOKllrL9ckvGhdTBNY8+cdYR8tthwSnXVi7a HTXcyfDJspvVz2i3OfDaXVRQ1A== X-Google-Smtp-Source: AFSGD/U/bqDUzoB03b3/Sn97hzwOKJJPGBzJxjjLwXi85jyaXzd+6v+6rI7hNTbDEd4bPLTcACr3Rw== X-Received: by 2002:a1c:1112:: with SMTP id 18mr10315704wmr.30.1544429443709; Mon, 10 Dec 2018 00:10:43 -0800 (PST) Received: from bhalevy-lt (system.cloudius-systems.com. [199.203.229.89]) by smtp.gmail.com with ESMTPSA id o81sm16772282wmd.10.2018.12.10.00.10.42 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 10 Dec 2018 00:10:43 -0800 (PST) Message-ID: Subject: Re: [PATCH 15/26] aio: support for IO polling From: Benny Halevy To: Jens Axboe , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org Cc: hch@lst.de, jmoyer@redhat.com, clm@fb.com Date: Mon, 10 Dec 2018 10:10:41 +0200 In-Reply-To: References: <20181207222016.29387-1-axboe@kernel.dk> <20181207222016.29387-16-axboe@kernel.dk> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.2 (3.30.2-2.fc29) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Sun, 2018-12-09 at 07:36 -0700, Jens Axboe wrote: > 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 Right. We'll break from the loop in this case. > 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. >