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 4879AC4BA06 for ; Wed, 26 Feb 2020 03:05:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 22B2D21744 for ; Wed, 26 Feb 2020 03:05:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729226AbgBZDFZ (ORCPT ); Tue, 25 Feb 2020 22:05:25 -0500 Received: from szxga06-in.huawei.com ([45.249.212.32]:57092 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727880AbgBZDFZ (ORCPT ); Tue, 25 Feb 2020 22:05:25 -0500 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 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org 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 . > . >