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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D56EAC433EF for ; Thu, 17 Mar 2022 23:16:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229591AbiCQXSJ (ORCPT ); Thu, 17 Mar 2022 19:18:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56460 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229447AbiCQXSI (ORCPT ); Thu, 17 Mar 2022 19:18:08 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AA8AD1A7706 for ; Thu, 17 Mar 2022 16:16:50 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id z15-20020a25bb0f000000b00613388c7d99so5605526ybg.8 for ; Thu, 17 Mar 2022 16:16:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=hvoW0T1Jxa8buR1vUq7mHDbmRrmWB7evEEmXb00k+lk=; b=EtXmvJO9en2amaPkrnmu4Xi2E9HoWfDQIP1qHWBhasehZ0Js3ng9DDzb3y9dipxnUB tJkMpUjlnXmmQG8+/Z4NjP4BaY71AfTo28LuJepcfxKRJR1ERDZwTcZ+v8ZLC5SUXC4z 2JED2DjpEw+go1rHx758n8RKcI+UaiCQ3diW1EtbbwWTUhn3qJYsl7r1pBROGXmWyuoT 492o3BveZFBpi49Uuy90Z8h/USxSqgmJ67+bVC2J7KOlr3LWLvj2z1HDXM8ePZMaqzwE v5QwAMqFnE5DUR+G0ntw2c93sWJ/vBYfOdE9uzdPzhDXHoDK2sAdQ/6vRHpepqKpvSu3 CQlQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=hvoW0T1Jxa8buR1vUq7mHDbmRrmWB7evEEmXb00k+lk=; b=eruN4IiSjmDcrekA5bhqj8hh2aRjFK6lTyino63tOfs5RzS3kVAA6MLgcd3/iy6h01 jCgQ0plT0k8g+y4o5kGHMsQW8lLOO0fe+i179T3sUNH/w0QiF2E3V8pX1FnPsmcFTuE9 uLDMmpNRDy42wY7g0ykIek44+qHSen+IOAiYn2ss8zli7INk3UI6VnJDyYrCBdXJn1XW a/+ss0odaP+0yvJAyUNYqRhQEyji4dyr2pPC34gDAQBR+m+jIEGFGm4WyeItJVg8RA1F 8Vf/50pemS4P+AFyWoEjdy7SzXQNclrRxKdPsDA7XDa7O8JQJKleCk6jfU4MzBz4h+8z zZRA== X-Gm-Message-State: AOAM530IYkb7kuR8qgPAHLRD8IoEv97GVboMaD+NImS+LVbSOfVn3Ld/ RY5+lLyAamdLtnHrfFD6eNbFA8Qg6kE0 X-Google-Smtp-Source: ABdhPJxiYWuxPZ+gOFx5nyIRI2ACj30mUOekasrtLlPHsJhLpmg75DvxfbzQm+haX3k7arH+uIq5nFB7RPmr X-Received: from irogers.svl.corp.google.com ([2620:15c:2cd:202:6811:1685:e3b9:7904]) (user=irogers job=sendgmr) by 2002:a25:cf47:0:b0:633:854f:b710 with SMTP id f68-20020a25cf47000000b00633854fb710mr7499660ybg.475.1647559009908; Thu, 17 Mar 2022 16:16:49 -0700 (PDT) Date: Thu, 17 Mar 2022 16:16:43 -0700 Message-Id: <20220317231643.550902-1-irogers@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.35.1.894.gb6a874cedc-goog Subject: [PATCH v2] perf evlist: Avoid iteration for empty evlist. From: Ian Rogers To: Arnaldo Carvalho de Melo , Namhyung Kim , Jiri Olsa , Adrian Hunter , Linux Kernel Mailing List Cc: Ian Rogers Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org As seen with 'perf stat --null ..' and reported in: https://lore.kernel.org/lkml/YjCLcpcX2peeQVCH@kernel.org/ v2. Avoids setting evsel in the empty list case as suggested by Jiri Olsa . Fixes: 472832d2c000 ("perf evlist: Refactor evlist__for_each_cpu()") Signed-off-by: Ian Rogers --- tools/perf/util/evlist.c | 28 +++++++++++++++++----------- 1 file changed, 17 insertions(+), 11 deletions(-) diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c index 8134d45e2164..9bb79e049957 100644 --- a/tools/perf/util/evlist.c +++ b/tools/perf/util/evlist.c @@ -346,7 +346,7 @@ struct evlist_cpu_iterator evlist__cpu_begin(struct evlist *evlist, struct affin { struct evlist_cpu_iterator itr = { .container = evlist, - .evsel = evlist__first(evlist), + .evsel = NULL, .cpu_map_idx = 0, .evlist_cpu_map_idx = 0, .evlist_cpu_map_nr = perf_cpu_map__nr(evlist->core.all_cpus), @@ -354,16 +354,22 @@ struct evlist_cpu_iterator evlist__cpu_begin(struct evlist *evlist, struct affin .affinity = affinity, }; - if (itr.affinity) { - itr.cpu = perf_cpu_map__cpu(evlist->core.all_cpus, 0); - affinity__set(itr.affinity, itr.cpu.cpu); - itr.cpu_map_idx = perf_cpu_map__idx(itr.evsel->core.cpus, itr.cpu); - /* - * If this CPU isn't in the evsel's cpu map then advance through - * the list. - */ - if (itr.cpu_map_idx == -1) - evlist_cpu_iterator__next(&itr); + if (evlist__empty(evlist)) { + /* Ensure the empty list doesn't iterate. */ + itr.evlist_cpu_map_idx = itr.evlist_cpu_map_nr; + } else { + itr.evsel = evlist__first(evlist); + if (itr.affinity) { + itr.cpu = perf_cpu_map__cpu(evlist->core.all_cpus, 0); + affinity__set(itr.affinity, itr.cpu.cpu); + itr.cpu_map_idx = perf_cpu_map__idx(itr.evsel->core.cpus, itr.cpu); + /* + * If this CPU isn't in the evsel's cpu map then advance + * through the list. + */ + if (itr.cpu_map_idx == -1) + evlist_cpu_iterator__next(&itr); + } } return itr; } -- 2.35.1.894.gb6a874cedc-goog