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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5A6BDC433F5 for ; Tue, 2 Nov 2021 11:05:45 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 284C660C41 for ; Tue, 2 Nov 2021 11:05:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 284C660C41 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:Cc:To:Subject:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=w+xgzMrI6dCwql6kJ/XVAtuc771xnqk3idXbjrtzg8Q=; b=D9CHH6XklTtWvivcNqot05VICu X0QQqUHHGaYc5mwwm7vC/o/UxwIga1rmIvorPgHT1j6K1PPhMoNC9iMWt/3XFxJx3aH6awvGupjzg AZqCkppIiI185KALWZAMxlM2BI9+2vpGGJbAXYId62mzrGVjSTFM40QPBE9F13VrNFE5hnsjvHCC6 ZlBfWQow19+90ze3mvIC1E+Y6/AVfzB/6mYImjIOhYJOZ2LWGTv0ITUGfEjUWCY41F8SiGEcvWLdH /3isnvgNKt5LqjWn5ApenqAYZbagDpzh0dZ/IupO2Lmbe41yVAeDr+9nyA/fhiwivO1+cB33kmJvO WNpQ7FYg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mhraI-001RHR-7Z; Tue, 02 Nov 2021 11:04:06 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mhrZH-001Qtn-8r for linux-arm-kernel@lists.infradead.org; Tue, 02 Nov 2021 11:03:05 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AE734D6E; Tue, 2 Nov 2021 04:03:01 -0700 (PDT) Received: from [10.57.46.25] (unknown [10.57.46.25]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 974903F70D; Tue, 2 Nov 2021 04:02:58 -0700 (PDT) Subject: Re: [PATCH 4/5] perf arm-spe: Implement find_snapshot callback To: Leo Yan Cc: Will Deacon , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, John Garry , Mathieu Poirier , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Mike Leach , linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org, James Clark References: <20210923135016.GG400258@leoy-ThinkPad-X240s> <20210923144048.GB603008@leoy-ThinkPad-X240s> <1c6a3a73-27dc-6673-7fe7-34bc7fcb0a68@arm.com> <20211004122724.GC174271@leoy-ThinkPad-X240s> <6b092f13-832f-5d1d-a504-aea96c81bf17@arm.com> <20211006095124.GC14400@leoy-ThinkPad-X240s> <377b54ef-b9c0-9cfc-ef0c-0187d7c493cc@arm.com> <20211013003916.GA130842@leoy-ThinkPad-X240s> <20211013075125.GA6701@willie-the-truck> <35209d5c-6387-5248-ab61-a1e1cb0553de@arm.com> <20211017061305.GA130233@leoy-ThinkPad-X240s> From: German Gomez Message-ID: <0f5f8911-ff80-db4f-3c0d-d172d39794c6@arm.com> Date: Tue, 2 Nov 2021 11:02:56 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20211017061305.GA130233@leoy-ThinkPad-X240s> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211102_040303_478619_8721746D X-CRM114-Status: GOOD ( 18.26 ) 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 Hi Leo, On 17/10/2021 07:13, Leo Yan wrote: > [...] > > I looked into the Arm SPE driver and found it doesn't really support > free run mode for AUX ring buffer when the driver runs in snapshot > mode, the pair functions perf_aux_output_end() and > perf_aux_output_begin() are invoked when every time handle the > interrupt. The detailed flow is: > > arm_spe_pmu_irq_handler() > `> arm_spe_pmu_buf_get_fault_act() > `> arm_spe_perf_aux_output_end() > `> set SPE registers > `> perf_aux_output_end() > `> arm_spe_perf_aux_output_begin() > `> perf_aux_output_begin() > `> set SPE registers > > Seems to me, a possible solution is to add an extra parameter 'int > in_interrupt' for functions arm_spe_perf_aux_output_end() and > arm_spe_perf_aux_output_begin(), if this parameter is passed as 1 in > the interrupt handling, these two functions should skip invoking > perf_aux_output_end() and perf_aux_output_begin() so can avoid the > redundant perf event PERF_RECORD_AUX. > > arm_spe_pmu_irq_handler() > `> arm_spe_pmu_buf_get_fault_act() > `> arm_spe_perf_aux_output_end(..., in_interrupt=1) > `> set SPE registers > `> arm_spe_perf_aux_output_begin(..., in_interrupt=1) > `> set SPE registers I brought the issue of the redundant AUX events to the team, and we know of at least one tool in Arm relying on these events in snapshot mode. So we think that changing this behavior of the driver might not be easy to do right now. > > P.s. I think Intel-PT has supported free run mode for snapshot mode, > so it should not generate interrupt in this mode. Thus Intel-PT can > avoid this issue, please see the code [2]. > > Thanks, > Leo > > [1] https://people.linaro.org/~leo.yan/spe/snapshot_test/perf.data > [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/events/intel/pt.c#n753 Thanks, German _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel