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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,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 A5E7CC3A589 for ; Tue, 20 Aug 2019 15:51:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7FC9F22DA9 for ; Tue, 20 Aug 2019 15:51:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730764AbfHTPvj (ORCPT ); Tue, 20 Aug 2019 11:51:39 -0400 Received: from out30-56.freemail.mail.aliyun.com ([115.124.30.56]:33957 "EHLO out30-56.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729827AbfHTPvj (ORCPT ); Tue, 20 Aug 2019 11:51:39 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R141e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04423;MF=luoben@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0Ta-xkxy_1566316283; Received: from bn0418deMacBook-Pro.local(mailfrom:luoben@linux.alibaba.com fp:SMTPD_---0Ta-xkxy_1566316283) by smtp.aliyun-inc.com(127.0.0.1); Tue, 20 Aug 2019 23:51:24 +0800 Subject: Re: [PATCH v3 0/3] genirq/vfio: Introduce update_irq_devid and optimize VFIO irq ops To: Alex Williamson Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org, tao.ma@linux.alibaba.com, gerry@linux.alibaba.com, nanhai.zou@linux.alibaba.com, linyunsheng@huawei.com References: <20190819145150.2d30669b@x1.home> <20190820092209.0c89effd@x1.home> From: luoben Message-ID: <4b2c76e3-91da-09b6-65f4-535828373c04@linux.alibaba.com> Date: Tue, 20 Aug 2019 23:51:23 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190820092209.0c89effd@x1.home> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2019/8/20 下午11:22, Alex Williamson 写道: > On Tue, 20 Aug 2019 12:03:50 +0800 > luoben wrote: > >> 在 2019/8/20 上午4:51, Alex Williamson 写道: >>> On Thu, 15 Aug 2019 21:02:58 +0800 >>> Ben Luo wrote: >>> >>>> Currently, VFIO takes a lot of free-then-request-irq actions whenever >>>> a VM (with device passthru via VFIO) sets irq affinity or mask/unmask >>>> irq. Those actions only change the cookie data of irqaction or even >>>> change nothing. The free-then-request-irq not only adds more latency, >>>> but also increases the risk of losing interrupt, which may lead to a >>>> VM hung forever in waiting for IO completion >>> What guest environment is generating this? Typically I don't see that >>> Windows or Linux guests bounce the interrupt configuration much. >>> Thanks, >>> >>> Alex >> By tracing centos5u8 on host, I found it keep masking and unmasking >> interrupt like this: >> >> [1566032533709879] index:28 irte_hi:000000010004a601 >> irte_lo:adb54bc000b98001 >> [1566032533711242] index:28 irte_hi:0000000000000000 >> irte_lo:0000000000000000 >> [1566032533711258] index:28 irte_hi:000000000004a601 >> irte_lo:00003fff00ac002d >> [1566032533711269] index:28 irte_hi:000000000004a601 >> irte_lo:00003fff00ac002d > [snip] >> "[1566032533720007]" is timestamp in μs, so centos5u8 tiggers 30+ irte >> modification within 10ms > Ok, that matches my understanding that only very old guests behave in > this manner. It's a curious case to optimize as RHEL5 is in extended > life-cycle support, with regular maintenance releases ending 2+ years > ago. Thanks, > > Alex But repeatedly set interrupt affinity in a new version guest can also cause the problem. Thanks,     Ben