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=-4.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 C8A34C433ED for ; Thu, 6 May 2021 11:47:00 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 6C827613CD for ; Thu, 6 May 2021 11:47:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6C827613CD 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=desiato.20200630; h=Sender:Content-Transfer-Encoding :Content-Type:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Subject:Cc:To: From:Message-ID:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=k4H2UzxOs3xhJ5fw2RvObGVgAamPkQlUrflqyfHKhlI=; b=Jtkm0AImRn7vETReoLHR4q6XF BPNpfV/su2zzfedO8qPrVd/hPczbVWRygACn/P94VWLRGthJ6dlBqVu5QGdB9kbqdbIBx/XOX6NFD xIe0kR6hO1CnOa2LT+BOBiFY8CLsVyU7cCoNsEBXB7AuQoqbOhCDC1wMH0b7Bot0uYIJOX0dbryMi +PxONkO7rzfhn47261VRXAmhuBMhaf4cxU3+gemH2oUcYSCQA/kUvQyRenm5abn2llPlUaE6uOFZq 4x+NlWOhjfdzvnxo5H5PIil95P08DFal5lKRxbBTHmMgcneczOnagesbVcLXu3m1lnqB8pDdOdp86 3pXyDIfTg==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lecQx-004A17-FM; Thu, 06 May 2021 11:44:47 +0000 Received: from bombadil.infradead.org ([2607:7c80:54:e::133]) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lecQv-004A0n-8w for linux-arm-kernel@desiato.infradead.org; Thu, 06 May 2021 11:44:45 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Type:MIME-Version:References: In-Reply-To:Subject:Cc:To:From:Message-ID:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=rjSyOWdrpasIifktchTN9DO06TA8wu+jxcqnKGGgP0g=; b=NxykEA1zC6i7TIwQhi1xP5aHEF XmPLK38qrPq3o/6t5WeNCUrZuKHJWyF/YzUS+Yoksn2kBTll0xospbeoFvvVK5M1HI/dHAFHIhyY2 YYp3wfi92yOMlzSaytn8AvO2Fgdi+cGljfwLVRntwNLJ7sUEZ30mfYiPXgJsVcXyeLYew/MiY4akv Gf/ipIizBgzv10w6/DhKr7rCRayF0YxIQkarcNL+UIws8haS9iArTZguRzEToslf7srTlgVxdUS6N cDqUIewTJ8rXml5crvsazk99WBzw55VPYsGd00G+bmk6llO5cKAJg6/aCXqeU7QHWw6kRxvnSuoYe PbZEn6rw==; Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lecQs-005zm8-Mj for linux-arm-kernel@lists.infradead.org; Thu, 06 May 2021 11:44:44 +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 29924610FC; Thu, 6 May 2021 11:44:42 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1lecQp-00BEVI-VJ; Thu, 06 May 2021 12:44:40 +0100 Date: Thu, 06 May 2021 12:44:21 +0100 Message-ID: <87pmy4qe7e.wl-maz@kernel.org> From: Marc Zyngier To: He Ying Cc: , , , , , , , , , , , , , , Subject: Re: [PATCH v3 03/16] arm64: Allow IPIs to be handled as normal interrupts In-Reply-To: References: User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: heying24@huawei.com, vincent.guittot@linaro.org, Valentin.Schneider@arm.com, andrew@lunn.ch, catalin.marinas@arm.com, f.fainelli@gmail.com, gregory.clement@bootlin.com, jason@lakedaemon.net, kernel-team@android.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux@arm.linux.org.uk, saravanak@google.com, sumit.garg@linaro.org, tglx@linutronix.de, will@kernel.org 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-20210506_044442_804546_E0DFF7AE X-CRM114-Status: GOOD ( 19.36 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, 06 May 2021 08:50:42 +0100, He Ying wrote: > > Hello Marc, > > We have faced a performance regression for handling ipis since this > commit. I think it's the same issue reported by Vincent. Can you share more details on what regression you have observed? What's the workload, the system, the performance drop? > I found you pointed out the possible two causes: > > (1) irq_enter/exit on the rescheduling IPI means we reschedule much > more often. It turned out to be a red herring. We don't reschedule more often, but we instead suffer from the overhead of irq_enter()/irq_exit(). However, this only matters for silly benchmarks, and no real-life workload showed any significant regression. Have you identified such realistic workload? > (2) irq_domain lookups add some overhead. While this is also a potential source of overhead, it turned out not to be the case. > But I don't see any following patches in mainline. So, are you still > working on this issue? Looking forward to your reply. See [1]. However, there is probably better things to do than this low-level specialisation of IPIs, and Thomas outlined what needs to be done (see v1 of the patch series). Thanks, M. [1] https://lore.kernel.org/lkml/20201124141449.572446-1-maz@kernel.org/ -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel