From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f171.google.com ([209.85.192.171]:40717 "EHLO mail-pf0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751494AbeBTWhM (ORCPT ); Tue, 20 Feb 2018 17:37:12 -0500 Received: by mail-pf0-f171.google.com with SMTP id m5so2423035pff.7 for ; Tue, 20 Feb 2018 14:37:12 -0800 (PST) Subject: Re: [PATCH] blk: optimization for classic polling To: Peter Zijlstra , Nitesh Shetty Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, joshi.k@samsung.com References: <3578876466-3733-1-git-send-email-nj.shetty@samsung.com> <20180220132137.GG25314@hirez.programming.kicks-ass.net> From: Jens Axboe Message-ID: <35a2d52e-dd40-d130-85d9-5f3ffe0d28af@kernel.dk> Date: Tue, 20 Feb 2018 12:37:07 -1000 MIME-Version: 1.0 In-Reply-To: <20180220132137.GG25314@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 2/20/18 3:21 AM, Peter Zijlstra wrote: > On Sun, May 30, 2083 at 09:51:06AM +0530, Nitesh Shetty wrote: >> This removes the dependency on interrupts to wake up task. Set task >> state as TASK_RUNNING, if need_resched() returns true, >> while polling for IO completion. >> Earlier, polling task used to sleep, relying on interrupt to wake it up. >> This made some IO take very long when interrupt-coalescing is enabled in >> NVMe. > > This is a horrible Changelog.. it does not in fact explain why the patch > works or is correct. Yeah, that should have been improved. > Also, set_current_state(TASK_RUNNING) is dodgy (similarly in > __blk_mq_poll), why do you need that memory barrier? I pointed that out in the review, and v2 fixed it. v2 is the one that got merged. -- Jens Axboe