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=-9.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 78A71C388F9 for ; Tue, 27 Oct 2020 10:38:27 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0EEFF22281 for ; Tue, 27 Oct 2020 10:38:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="bgXYb8PH"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="ByIyJYnP" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0EEFF22281 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Message-ID:References:In-Reply-To:Subject:To:From: Date:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=nlIqvMR5l+jn6V0bf9K1AYHIA2nhypnsbkqoVsDte2E=; b=bgXYb8PHnWc4yjqhK7qiQGe4j J9gT+zKR3vlagdEPckBEVWmYVdAMhq4/zUrgzfb9A/RWmrONL+ggOrRnOYO6pwKhmRMgqNVjeRNNP HDIjYuq20AifqIIRzokldUlzCD3zyZsAoQwuHeiVY2+u0kXzmYVO2ve+OdKIdp67wwfvVUKhfa4no PmAp3BDmW00diZ2t1Wcg7Gbr3NKNisi294AWeGKsGXZcdKIV0xVnat//A2nwhdxFvehdZhOTFfnYv GE5e2VlPVtmiUi9B5/6dT1xe28NMgzQoZDXoQRM9x4gqFIZuD974W6cQSn0sim8uLfUcqoi7aanAs 9Ynxjbs0Q==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kXMMX-0008LC-0P; Tue, 27 Oct 2020 10:37:57 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kXMMF-0008H1-UR for linux-arm-kernel@lists.infradead.org; Tue, 27 Oct 2020 10:37:41 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EEEE220780; Tue, 27 Oct 2020 10:37:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603795058; bh=OcnUMuBA901Kxhgnt8GvlIDOQoOTk8b7CBTnQqnMdA8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ByIyJYnP5TAv58na/z32RMBoNQLgO1yRlAqQcGR9525dLfUziBthSg+Co5jEVdMD2 W4tzYJ+b8d3ayNdzu0R7d1OrhEwgPKGE7uCPJgAtB9oaUaJXkaOML43XwzJ4zO/8sR WiLVnMc3T66iXivOM/IoLHBB7+/CBhI6jpHtxJoo= Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1kXMMB-004eav-WC; Tue, 27 Oct 2020 10:37:36 +0000 MIME-Version: 1.0 Date: Tue, 27 Oct 2020 10:37:35 +0000 From: Marc Zyngier To: Vincent Guittot Subject: Re: [PATCH v3 03/16] arm64: Allow IPIs to be handled as normal interrupts In-Reply-To: References: <20200901144324.1071694-1-maz@kernel.org> <20200901144324.1071694-4-maz@kernel.org> <353f13b0dcc6c7ea1b44012d9632a0cc@kernel.org> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <7b754dfe579044902d3468b9f864bd37@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: vincent.guittot@linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, will@kernel.org, catalin.marinas@arm.com, linux@arm.linux.org.uk, tglx@linutronix.de, jason@lakedaemon.net, sumit.garg@linaro.org, Valentin.Schneider@arm.com, f.fainelli@gmail.com, gregory.clement@bootlin.com, andrew@lunn.ch, saravanak@google.com, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201027_063740_185404_02BE06F8 X-CRM114-Status: GOOD ( 24.52 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Sumit Garg , Android Kernel Team , Florian Fainelli , Russell King , Jason Cooper , Saravana Kannan , Andrew Lunn , Catalin Marinas , Gregory Clement , linux-kernel , Thomas Gleixner , Will Deacon , Valentin Schneider , LAK Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2020-10-27 10:12, Vincent Guittot wrote: > HI Marc, > > On Mon, 19 Oct 2020 at 17:43, Vincent Guittot > wrote: >> >> On Mon, 19 Oct 2020 at 15:04, Marc Zyngier wrote: >> > > > ... > >> > >> >> > >> One of the major difference is that we end up, in some cases >> > >> (such as when performing IRQ time accounting on the scheduler >> > >> IPI), end up with nested irq_enter()/irq_exit() pairs. >> > >> Other than the (relatively small) overhead, there should be >> > >> no consequences to it (these pairs are designed to nest >> > >> correctly, and the accounting shouldn't be off). >> > > >> > > While rebasing on mainline, I have faced a performance regression for >> > > the benchmark: >> > > perf bench sched pipe >> > > on my arm64 dual quad core (hikey) and my 2 nodes x 112 CPUS (thx2) >> > > >> > > The regression comes from: >> > > commit: d3afc7f12987 ("arm64: Allow IPIs to be handled as normal >> > > interrupts") >> > >> > That's interesting, as this patch doesn't really change anything (most >> > of the potential overhead comes in later). The only potential overhead >> > I can see is that the scheduler_ipi() call is now wrapped around >> > irq_enter()/irq_exit(). >> > >> > > >> > > v5.9 + this patch >> > > hikey : 48818(+/- 0.31) 37503(+/- 0.15%) -23.2% >> > > thx2 : 132410(+/- 1.72) 122646(+/- 1.92%) -7.4% >> > > >> > > By + this patch, I mean merging branch from this patch. Whereas >> > > merging the previous: >> > > commit: 83cfac95c018 ("genirq: Allow interrupts to be excluded from >> > > /proc/interrupts") >> > > It doesn't show any regression >> > >> > Since you are running perf, can you spot where the overhead occurs? > > Any idea about the root cause of the regression ? > I have faced it on more arm64 platforms in the meantime two possible causes: (1) irq_enter/exit on the rescheduling IPI means we reschedule much more often (2) irq_domain lookups add some overhead. For (1), I have this series[1] which is ugly as sin and needs much more testing. For (2), I have some ideas which need more work (let the irq domain resolve to an irq_desc instead of an interrupt number, avoiding another radix-tree lookup). M. [1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=irq/ipi-fixes -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel