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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,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 11B07C433B4 for ; Wed, 28 Apr 2021 07:01:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF610610F7 for ; Wed, 28 Apr 2021 07:01:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233698AbhD1HCY convert rfc822-to-8bit (ORCPT ); Wed, 28 Apr 2021 03:02:24 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:3093 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229643AbhD1HCX (ORCPT ); Wed, 28 Apr 2021 03:02:23 -0400 Received: from dggeml759-chm.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4FVTwL6RFxzWZJP; Wed, 28 Apr 2021 14:57:38 +0800 (CST) Received: from dggemi709-chm.china.huawei.com (10.3.20.108) by dggeml759-chm.china.huawei.com (10.1.199.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Wed, 28 Apr 2021 15:01:35 +0800 Received: from dggemi761-chm.china.huawei.com (10.1.198.147) by dggemi709-chm.china.huawei.com (10.3.20.108) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Wed, 28 Apr 2021 15:01:35 +0800 Received: from dggemi761-chm.china.huawei.com ([10.9.49.202]) by dggemi761-chm.china.huawei.com ([10.9.49.202]) with mapi id 15.01.2176.012; Wed, 28 Apr 2021 15:01:35 +0800 From: "Song Bao Hua (Barry Song)" To: Feng Tang , Thomas Gleixner CC: kernel test robot , Ingo Molnar , LKML , "lkp@lists.01.org" , "lkp@intel.com" , "ying.huang@intel.com" , "zhengjun.xing@intel.com" , "x86@kernel.org" Subject: RE: [genirq] cbe16f35be: will-it-scale.per_thread_ops -5.2% regression Thread-Topic: [genirq] cbe16f35be: will-it-scale.per_thread_ops -5.2% regression Thread-Index: AQHXO0FhMjEcPgOF502NS90b4qVMhqrHuBoAgAEkLwCAAKN1wA== Date: Wed, 28 Apr 2021 07:01:35 +0000 Message-ID: References: <20210427090013.GG32408@xsang-OptiPlex-9020> <87fszcnecr.ffs@nanos.tec.linutronix.de> <20210428050758.GB52098@shbuild999.sh.intel.com> In-Reply-To: <20210428050758.GB52098@shbuild999.sh.intel.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.126.202.171] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > -----Original Message----- > From: Feng Tang [mailto:feng.tang@intel.com] > Sent: Wednesday, April 28, 2021 5:08 PM > To: Thomas Gleixner > Cc: kernel test robot ; Song Bao Hua (Barry Song) > ; Ingo Molnar ; LKML > ; lkp@lists.01.org; lkp@intel.com; > ying.huang@intel.com; zhengjun.xing@intel.com; x86@kernel.org > Subject: Re: [genirq] cbe16f35be: will-it-scale.per_thread_ops -5.2% > regression > > Hi Thomas, > > On Tue, Apr 27, 2021 at 01:42:12PM +0200, Thomas Gleixner wrote: > > Folks, > > > > On Tue, Apr 27 2021 at 17:00, kernel test robot wrote: > > > > > Greeting, > > > > > > FYI, we noticed a -5.2% regression of will-it-scale.per_thread_ops due to > commit: > > > > > > commit: cbe16f35bee6880becca6f20d2ebf6b457148552 ("genirq: Add > > > IRQF_NO_AUTOEN for request_irq/nmi()") > > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git > > > master > > > > this is the second report in the last week which makes not a lot of sense. > > And this oneis makes absolutely no sense at all. > > > > This commit affects request_irq() and the related variants and has > > exactly ZERO influence on anything related to that test case simply > > because. > > > > I seriously have to ask the question whether this test infrastructure > > is actually measuring what it claims to measure. > > > > As this commit clearly _cannot_ have the 'measured' side effect, this > > points to some serious issue in the tests or the test infrastructure > > itself. > > 0day has reported about 20 similar cases that the bisected commit has nothing > to do with the benchmark case, and we were very confused too back then. And > our debug showed many of them changed the code alignment of kernel data or text > of other modules which is relevant with the benchmark, though some cases are > not well explained yet. Following are links of some explained cases. > > https://lore.kernel.org/lkml/20200305062138.GI5972@shao2-debian/ > https://lore.kernel.org/lkml/20200330011254.GA14393@feng-iot/ > https://lore.kernel.org/lkml/20201102091543.GM31092@shao2-debian/ > > And to debug code alignment case, one debug patch to force all function address > aligned to 32 bytes was merged in v5.9 > > 09c60546f04f ./Makefile: add debug option to enable function aligned on 32 bytes > > > For this particular case, the commit changes the code size of > request_threaded_irq(), and many following functions' alignment are changed. > If so, the performance impact of code change would be random. > So I extended the debug patch to force 64 bytes aligned, then this commit will > cause _no_ performance change for the same test case on same platform. > > diff --git a/Makefile b/Makefile > > ifdef CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_32B > -KBUILD_CFLAGS += -falign-functions=32 > +KBUILD_CFLAGS += -falign-functions=64 > endif > > Though I don't know the detail of how exactly this code alignment affects the > case. Guess it is related with icache. But it is still an irrelevant problem. > > Thanks, > Feng > > > Thanks, > > > > tglx Thanks Barry