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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 A985BC433DF for ; Tue, 26 May 2020 08:08:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8017820663 for ; Tue, 26 May 2020 08:08:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="QnWzARIv" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731413AbgEZIIB (ORCPT ); Tue, 26 May 2020 04:08:01 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:27337 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726926AbgEZIIB (ORCPT ); Tue, 26 May 2020 04:08:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590480475; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4qPuy21thUmWYvEWAv8ubPfXDGwVw2Do/ZSlrhPm0P4=; b=QnWzARIvUXD76nXu8lLTHQ8DdTRPy7eVfoRLx3saz/9LpUNUWzwmp0OHfQkvU+kZBxBti3 cmLozKfjCl7kKdVzgiz5R2fAapL1/UgSsvK0trkIRhAhcOmqXoAJ3hvTLsdd1mERmUFNw9 Z5ZezqVcGMl7Eooe0VO4rGcQtYwXXIw= 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-3-UMV5ZecxOJ6Rb2WnsxjQJg-1; Tue, 26 May 2020 04:07:54 -0400 X-MC-Unique: UMV5ZecxOJ6Rb2WnsxjQJg-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 C51AF460; Tue, 26 May 2020 08:07:52 +0000 (UTC) Received: from [10.36.114.116] (ovpn-114-116.ams2.redhat.com [10.36.114.116]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 874D15D9E5; Tue, 26 May 2020 08:07:45 +0000 (UTC) From: "Eelco Chaudron" To: "Andrii Nakryiko" Cc: bpf , "David S. Miller" , Networking , "Alexei Starovoitov" , "Daniel Borkmann" , "Martin Lau" , "Song Liu" , "Yonghong Song" , "Andrii Nakryiko" , "Toke =?utf-8?b?SMO4aWxhbmQtSsO4cmdlbnNlbg==?=" Subject: Re: [PATCH bpf-next] libbpf: add API to consume the perf ring buffer content Date: Tue, 26 May 2020 10:07:42 +0200 Message-ID: <51FAF2C0-F843-45EF-8CE7-69FD0334AD84@redhat.com> In-Reply-To: References: <159042332675.79900.6845937535091126683.stgit@ebuild> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 26 May 2020, at 7:29, Andrii Nakryiko wrote: > On Mon, May 25, 2020 at 2:01 PM Eelco Chaudron > wrote: >> >> This new API, perf_buffer__consume, can be used as follows: > > I wonder, was it inspired by yet-to-be committed > ring_buffer__consume() or it's just a coincidence? Just coincidence, I was needing a function to flush the remaining ring entries, as I was using a larger wakeup_events value. Initially, I called the function ring_buffer_flush(), but once I noticed your patch I renamed it :) >> - When you have a perf ring where wakeup_events is higher than 1, >> and you have remaining data in the rings you would like to pull >> out on exit (or maybe based on a timeout). >> - For low latency cases where you burn a CPU that constantly polls >> the queues. >> >> Signed-off-by: Eelco Chaudron >> --- >> tools/lib/bpf/libbpf.c | 23 +++++++++++++++++++++++ >> tools/lib/bpf/libbpf.h | 1 + >> tools/lib/bpf/libbpf.map | 1 + >> 3 files changed, 25 insertions(+) >> >> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c >> index fa04cbe547ed..cbef3dac7507 100644 >> --- a/tools/lib/bpf/libbpf.c >> +++ b/tools/lib/bpf/libbpf.c >> @@ -8456,6 +8456,29 @@ int perf_buffer__poll(struct perf_buffer *pb, >> int timeout_ms) >> return cnt < 0 ? -errno : cnt; >> } >> >> +int perf_buffer__consume(struct perf_buffer *pb) >> +{ >> + int i; >> + >> + if (!pb) >> + return -EINVAL; > > we don't check this in perf_buffer__poll, IMO, checking this in every > "method" is an overkill. Ack, will fix in v2 >> + >> + if (!pb->cpu_bufs) >> + return 0; > > no need to check. It's either non-NULL for valid perf_buffer, or > calloc could return NULL if pb->cpu_cnt is zero (not sure it's > possible, but still), but then loop below will never access > pb->cpu_bufs[i]. Agreed, was just adding some safety checks, but in the constantly poll mode this is a lot of overhead. Will remover in v2. >> + >> + for (i = 0; i < pb->cpu_cnt && pb->cpu_bufs[i]; i++) { > > I think pb->cpu_bufs[i] check is wrong, it will stop iteration > prematurely if cpu_bufs are sparsely populated. So move check inside > and continue loop if NULL. Mimicked the behavior from other functions, however just to be safe I split it up. >> + int err; > > nit: declare it together with "i" above, similar to how > perf_buffer__poll does it Put it down here as it’s only used in the context of the for loop, but will move it up in the v2. >> + struct perf_cpu_buf *cpu_buf = pb->cpu_bufs[i]; >> + >> + err = perf_buffer__process_records(pb, cpu_buf); >> + if (err) { >> + pr_warn("error while processing records: >> %d\n", err); >> + return err; >> + } >> + } >> + return 0; >> +} >> + >> struct bpf_prog_info_array_desc { >> int array_offset; /* e.g. offset of jited_prog_insns */ >> int count_offset; /* e.g. offset of jited_prog_len */ >> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h >> index 8ea69558f0a8..1e2e399a5f2c 100644 >> --- a/tools/lib/bpf/libbpf.h >> +++ b/tools/lib/bpf/libbpf.h >> @@ -533,6 +533,7 @@ perf_buffer__new_raw(int map_fd, size_t page_cnt, >> >> LIBBPF_API void perf_buffer__free(struct perf_buffer *pb); >> LIBBPF_API int perf_buffer__poll(struct perf_buffer *pb, int >> timeout_ms); >> +LIBBPF_API int perf_buffer__consume(struct perf_buffer *pb); >> >> typedef enum bpf_perf_event_ret >> (*bpf_perf_event_print_t)(struct perf_event_header *hdr, >> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map >> index 0133d469d30b..381a7342ecfc 100644 >> --- a/tools/lib/bpf/libbpf.map >> +++ b/tools/lib/bpf/libbpf.map >> @@ -262,4 +262,5 @@ LIBBPF_0.0.9 { >> bpf_link_get_fd_by_id; >> bpf_link_get_next_id; >> bpf_program__attach_iter; >> + perf_buffer__consume; >> } LIBBPF_0.0.8; >> Thanks for the review, will send out a v2 soon.