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 0669BC433F5 for ; Fri, 15 Oct 2021 12:33:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DBED961090 for ; Fri, 15 Oct 2021 12:33:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235668AbhJOMf4 (ORCPT ); Fri, 15 Oct 2021 08:35:56 -0400 Received: from foss.arm.com ([217.140.110.172]:41970 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234372AbhJOMfv (ORCPT ); Fri, 15 Oct 2021 08:35:51 -0400 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 4D9E1147A; Fri, 15 Oct 2021 05:33:44 -0700 (PDT) Received: from [10.57.73.178] (unknown [10.57.73.178]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A18913F70D; Fri, 15 Oct 2021 05:33:41 -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: <20210916154635.1525-1-german.gomez@arm.com> <20210916154635.1525-4-german.gomez@arm.com> <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> From: German Gomez Message-ID: <35209d5c-6387-5248-ab61-a1e1cb0553de@arm.com> Date: Fri, 15 Oct 2021 13:33:39 +0100 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: <20211013075125.GA6701@willie-the-truck> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Leo, Would you be ok with the current patch the way it is? In case it's of any help, I'm sharing the testing steps that James and I went through when testing this internally, if you want to add to it - Test that only a portion of the buffer is saved until there is a wraparound $ ./perf record -vvv -e arm_spe/period=148576/u -S -- taskset --cpu-list 0 stress --cpu 1 & while true; do sleep 0.2; killall -s USR2 perf; done - Test snapshot mode in CPU mode $ sudo ./perf record -vvv -C 0 -e arm_spe/period=148576/u -S -- taskset --cpu-list 0 stress --cpu 1 & - Test that auxtrace buffers correspond to an aux record - Test snapshot default sizes in sudo and user modes - Test small snapshot size $ ./perf record -vvv -e arm_spe/period=148576/u -S1000 -m16,16 -- taskset --cpu-list 0 stress --cpu 1 & If there are any concerns with the patches, please let me know and I will try to address them. Thanks, German On 13/10/2021 08:51, Will Deacon wrote: > On Wed, Oct 13, 2021 at 08:39:16AM +0800, Leo Yan wrote: >> On Mon, Oct 11, 2021 at 04:55:37PM +0100, German Gomez wrote: >>> On 06/10/2021 10:51, Leo Yan wrote: >>>> On Wed, Oct 06, 2021 at 10:35:20AM +0100, German Gomez wrote: >>>> >>>> [...] >>>> >>>>>> So simply say, I think the head pointer monotonically increasing is >>>>>> the right thing to do in Arm SPE driver. >>>>> I will talk to James about how we can proceed on this. >>>> Thanks! >>> I took this offline with James and, though it looks possible to patch >>> the SPE driver to have a monotonically increasing head pointer in order >>> to simplify the handling in the perf tool, it could be a breaking change >>> for users of the perf_event_open syscall that currently rely on the way >>> it works now. >> Here I cannot create the connection between AUX head pointer and the >> breakage of calling perf_event_open(). >> >> Could you elaborate what's the reason the monotonical increasing head >> pointer will lead to the breakage for perf_event_open()? > It's a user-visible change in behaviour, isn't it? Therefore we risk > breaking applications that rely on the current behaviour if we change it > unconditionally. > > Given that the driver has always worked like this and it doesn't sound like > it's the end of the world to deal with it in userspace (after all, it's > aligned with intel-pt), then I don't think we should change it. > > Will 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 148D2C433EF for ; Fri, 15 Oct 2021 12:35:14 +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 D13E060F36 for ; Fri, 15 Oct 2021 12:35:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org D13E060F36 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=67KUtx6gwpBRdEUR1jLrg03gdrR0fBf1WC9VCw7+AZU=; b=aSG8oiXscHK6HchcxiwufcgQgt Fr1xyGSk+LzIcdY/TEvFHkjPsncfRbn6X1RfyMBvExOgd4CyUVJJAR5z6xIP9ByjFqzYqkF29tJur kafFBnLateUcEk4FlwK/nufu7AvVYTrwGMBnr4U6jviniTGqV8lzKVSEJGf5QOC19bUZdnhRCLCJA DNAsqbhPuwRAZgJ4UezOWSPGQ8CSUFKwMEKvmKZLxCX7cbry5P+Uu4X/hC+rMJ57mF0Qf1yjBbU3z /MToz0/9MtGRYmH4iF9wMe1S3XFCaMdnPXYsGmZakFOJYnvsba2SMM1DzfNzLLtgCzvPnoYS+a2Df Ka41xKhA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mbMPK-006vC3-0W; Fri, 15 Oct 2021 12:33:54 +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 1mbMPF-006vAC-Lb for linux-arm-kernel@lists.infradead.org; Fri, 15 Oct 2021 12:33:51 +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 4D9E1147A; Fri, 15 Oct 2021 05:33:44 -0700 (PDT) Received: from [10.57.73.178] (unknown [10.57.73.178]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A18913F70D; Fri, 15 Oct 2021 05:33:41 -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: <20210916154635.1525-1-german.gomez@arm.com> <20210916154635.1525-4-german.gomez@arm.com> <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> From: German Gomez Message-ID: <35209d5c-6387-5248-ab61-a1e1cb0553de@arm.com> Date: Fri, 15 Oct 2021 13:33:39 +0100 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: <20211013075125.GA6701@willie-the-truck> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211015_053349_836495_F1C98632 X-CRM114-Status: GOOD ( 23.69 ) 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, Would you be ok with the current patch the way it is? In case it's of any help, I'm sharing the testing steps that James and I went through when testing this internally, if you want to add to it - Test that only a portion of the buffer is saved until there is a wraparound $ ./perf record -vvv -e arm_spe/period=148576/u -S -- taskset --cpu-list 0 stress --cpu 1 & while true; do sleep 0.2; killall -s USR2 perf; done - Test snapshot mode in CPU mode $ sudo ./perf record -vvv -C 0 -e arm_spe/period=148576/u -S -- taskset --cpu-list 0 stress --cpu 1 & - Test that auxtrace buffers correspond to an aux record - Test snapshot default sizes in sudo and user modes - Test small snapshot size $ ./perf record -vvv -e arm_spe/period=148576/u -S1000 -m16,16 -- taskset --cpu-list 0 stress --cpu 1 & If there are any concerns with the patches, please let me know and I will try to address them. Thanks, German On 13/10/2021 08:51, Will Deacon wrote: > On Wed, Oct 13, 2021 at 08:39:16AM +0800, Leo Yan wrote: >> On Mon, Oct 11, 2021 at 04:55:37PM +0100, German Gomez wrote: >>> On 06/10/2021 10:51, Leo Yan wrote: >>>> On Wed, Oct 06, 2021 at 10:35:20AM +0100, German Gomez wrote: >>>> >>>> [...] >>>> >>>>>> So simply say, I think the head pointer monotonically increasing is >>>>>> the right thing to do in Arm SPE driver. >>>>> I will talk to James about how we can proceed on this. >>>> Thanks! >>> I took this offline with James and, though it looks possible to patch >>> the SPE driver to have a monotonically increasing head pointer in order >>> to simplify the handling in the perf tool, it could be a breaking change >>> for users of the perf_event_open syscall that currently rely on the way >>> it works now. >> Here I cannot create the connection between AUX head pointer and the >> breakage of calling perf_event_open(). >> >> Could you elaborate what's the reason the monotonical increasing head >> pointer will lead to the breakage for perf_event_open()? > It's a user-visible change in behaviour, isn't it? Therefore we risk > breaking applications that rely on the current behaviour if we change it > unconditionally. > > Given that the driver has always worked like this and it doesn't sound like > it's the end of the world to deal with it in userspace (after all, it's > aligned with intel-pt), then I don't think we should change it. > > Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel