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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 5686AC4BA06 for ; Wed, 26 Feb 2020 03:05:29 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2392A21744 for ; Wed, 26 Feb 2020 03:05:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2392A21744 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A21BC6B0003; Tue, 25 Feb 2020 22:05:28 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9A9B86B0005; Tue, 25 Feb 2020 22:05:28 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 872156B0006; Tue, 25 Feb 2020 22:05:28 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0184.hostedemail.com [216.40.44.184]) by kanga.kvack.org (Postfix) with ESMTP id 6BCD66B0003 for ; Tue, 25 Feb 2020 22:05:28 -0500 (EST) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 2259D4995FF for ; Wed, 26 Feb 2020 03:05:28 +0000 (UTC) X-FDA: 76530787536.04.bird83_2fab157573e4b X-HE-Tag: bird83_2fab157573e4b X-Filterd-Recvd-Size: 3031 Received: from huawei.com (szxga06-in.huawei.com [45.249.212.32]) by imf33.hostedemail.com (Postfix) with ESMTP for ; Wed, 26 Feb 2020 03:05:27 +0000 (UTC) Received: from DGGEMS412-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 782DE46488E95C5DEB79; Wed, 26 Feb 2020 11:05:22 +0800 (CST) Received: from [127.0.0.1] (10.67.101.242) by DGGEMS412-HUB.china.huawei.com (10.3.19.212) with Microsoft SMTP Server id 14.3.439.0; Wed, 26 Feb 2020 11:05:19 +0800 Subject: Re: [PATCH v4 03/26] iommu: Add a page fault handler To: Jean-Philippe Brucker References: <20200224182401.353359-1-jean-philippe@linaro.org> <20200224182401.353359-4-jean-philippe@linaro.org> <20200225092519.GC375953@myrica> CC: , , , , , , , Jean-Philippe Brucker , , , , , , , From: Xu Zaibo Message-ID: <0c2b29ad-d09a-89db-8540-5909751b1972@huawei.com> Date: Wed, 26 Feb 2020 11:05:19 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <20200225092519.GC375953@myrica> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.101.242] X-CFilter-Loop: Reflected X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi, On 2020/2/25 17:25, Jean-Philippe Brucker wrote: > Hi Zaibo, > > On Tue, Feb 25, 2020 at 11:30:05AM +0800, Xu Zaibo wrote: >>> +struct iopf_queue * >>> +iopf_queue_alloc(const char *name, iopf_queue_flush_t flush, void *cookie) >>> +{ >>> + struct iopf_queue *queue; >>> + >>> + queue = kzalloc(sizeof(*queue), GFP_KERNEL); >>> + if (!queue) >>> + return NULL; >>> + >>> + /* >>> + * The WQ is unordered because the low-level handler enqueues faults by >>> + * group. PRI requests within a group have to be ordered, but once >>> + * that's dealt with, the high-level function can handle groups out of >>> + * order. >>> + */ >>> + queue->wq = alloc_workqueue("iopf_queue/%s", WQ_UNBOUND, 0, name); >> Should this workqueue use 'WQ_HIGHPRI | WQ_UNBOUND' or some flags like this >> to decrease the unexpected >> latency of I/O PageFault here? Or maybe, workqueue will show an uncontrolled >> latency, even in a busy system. > I'll investigate the effect of these flags. So far I've only run on > completely idle systems but it would be interesting to add some > workqueue-heavy load in my tests. > I'm not sure, just my concern. Hopefully, Tejun Heo can give us some hints. :) +cc Tejun Heo Cheers, Zaibo . > . >