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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 46735C433E0 for ; Fri, 12 Mar 2021 12:13:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0398364FEA for ; Fri, 12 Mar 2021 12:13:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229918AbhCLMNM (ORCPT ); Fri, 12 Mar 2021 07:13:12 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:56464 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229532AbhCLMM5 (ORCPT ); Fri, 12 Mar 2021 07:12:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615551176; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=WwtaaYJsAPHM2MQ6ykC4hJpMyE8cn0R0tH+/nW3nDi0=; b=e9v33kfyLkcw93GUARor8mTZPeYVeDVCvzacokZmUdltnPtEEeP9CZCr8VWSiCAyfDooSL 1Lz6gtWfZrHqUv60fRxW0CY1NunErjGOrCj+8FKeBLMQtz6VGQJL0pyyMggzhDnUgosIRF 0CFzzqCo+1ioipKx/Bb0pZYWpCzF2MU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-4--aUv8mjAMf29uGRGbXbf8g-1; Fri, 12 Mar 2021 07:12:52 -0500 X-MC-Unique: -aUv8mjAMf29uGRGbXbf8g-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 49F3680006E; Fri, 12 Mar 2021 12:12:51 +0000 (UTC) Received: from krava (unknown [10.40.192.54]) by smtp.corp.redhat.com (Postfix) with SMTP id 775375DDAD; Fri, 12 Mar 2021 12:12:49 +0000 (UTC) Date: Fri, 12 Mar 2021 13:12:48 +0100 From: Jiri Olsa To: Song Liu Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, acme@kernel.org, acme@redhat.com, namhyung@kernel.org, jolsa@kernel.org Subject: Re: [PATCH] perf-stat: introduce bperf, share hardware PMCs with BPF Message-ID: References: <20210312020257.197137-1-songliubraving@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210312020257.197137-1-songliubraving@fb.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 11, 2021 at 06:02:57PM -0800, Song Liu wrote: > perf uses performance monitoring counters (PMCs) to monitor system > performance. The PMCs are limited hardware resources. For example, > Intel CPUs have 3x fixed PMCs and 4x programmable PMCs per cpu. > > Modern data center systems use these PMCs in many different ways: > system level monitoring, (maybe nested) container level monitoring, per > process monitoring, profiling (in sample mode), etc. In some cases, > there are more active perf_events than available hardware PMCs. To allow > all perf_events to have a chance to run, it is necessary to do expensive > time multiplexing of events. > > On the other hand, many monitoring tools count the common metrics (cycles, > instructions). It is a waste to have multiple tools create multiple > perf_events of "cycles" and occupy multiple PMCs. > > bperf tries to reduce such wastes by allowing multiple perf_events of > "cycles" or "instructions" (at different scopes) to share PMUs. Instead > of having each perf-stat session to read its own perf_events, bperf uses > BPF programs to read the perf_events and aggregate readings to BPF maps. > Then, the perf-stat session(s) reads the values from these BPF maps. > > Please refer to the comment before the definition of bperf_ops for the > description of bperf architecture. > > bperf is off by default. To enable it, pass --use-bpf option to perf-stat. > bperf uses a BPF hashmap to share information about BPF programs and maps > used by bperf. This map is pinned to bpffs. The default address is > /sys/fs/bpf/bperf_attr_map. The user could change the address with option > --attr-map. nice, I recall the presentation about that and was wondering when this will come up ;-) > > --- > Known limitations: > 1. Do not support per cgroup events; > 2. Do not support monitoring of BPF program (perf-stat -b); > 3. Do not support event groups. > > The following commands have been tested: > > perf stat --use-bpf -e cycles -a > perf stat --use-bpf -e cycles -C 1,3,4 > perf stat --use-bpf -e cycles -p 123 > perf stat --use-bpf -e cycles -t 100,101 I assume the output is same as standard perf? jirka