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=-13.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 24D0CC433DF for ; Mon, 25 May 2020 01:43:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ED56A20776 for ; Mon, 25 May 2020 01:43:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="mODj/zYa" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388294AbgEYBnN (ORCPT ); Sun, 24 May 2020 21:43:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39398 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728357AbgEYBnN (ORCPT ); Sun, 24 May 2020 21:43:13 -0400 Received: from mail-io1-xd44.google.com (mail-io1-xd44.google.com [IPv6:2607:f8b0:4864:20::d44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DDC59C05BD43 for ; Sun, 24 May 2020 18:43:12 -0700 (PDT) Received: by mail-io1-xd44.google.com with SMTP id q8so15855998iow.7 for ; Sun, 24 May 2020 18:43:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=aqz94/+7e1RiM5o+h+HIR5TE0upbQHfvoZz9aXKyiXs=; b=mODj/zYaEfVJeQKqnlvU8U0thUA054KETDD+0ZJLi/WUHfuJCiUK+YSmFFrpzDEb2T qfvn1pEwu7ZiV5+l6WMtrkMTLo5vrGse/ywkJHZgM302nWAn3p3P89mZ7AdaS5okO5z+ B0zQERPodLWyTeyc3I30uPgJtEMgR1Nk3d+XD3yOBFmh+1B9cEOpKQZlRARDCHFn0mO7 MWXJX34skcUgAi+UliZvPi6mvfe5Id4PHa7lQEJR9F2Ml57zrSYcjgO1bxTqd+lqQCpz vLdpgx9e++1DVTlk0l0QsBLh1xR07qXZH/cJFC69qYM58i7uTFqSHjreyKCnhqwwsKrt V5nQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=aqz94/+7e1RiM5o+h+HIR5TE0upbQHfvoZz9aXKyiXs=; b=grVk9i8GhKfsUh5Qgi/aPUsD3vDGFx3Es9tIPCcLi+KiYBlAf/TLgkczP02yulvGJ6 wlzXpdxIjVxspxcguUIohQoQSX60/y410cFkhxxdSLvMZajq9LetJFtf+izV7CH94wrd BELMGkuSVEcCQ8vSUIaKSw1Nh6DBp8W3Lb2rETX2N+1LDdj+fN5/7eg6xVB38qK+M88n CXcpSb6a2Cmdruq2znj1ERMHm7D2NF4B9AW09EUODs2WrS2eXEEAUdXRttDLaTGZ28wA 3chJt0tQ1raah42t+XAXYMRQsdFVBheo/urqmSJefKnuomJFHdw5kxeT27lB/ee0rZNv yFPg== X-Gm-Message-State: AOAM531gV6Yi3SOLsC/HWtCi9b4WSkzt/gQxtVg0UtiaCPlgBPTLlQQ+ ygYrsNZuZnbmLfz6spX3Rxzc78OaJR/cn9TvGsfe7w== X-Google-Smtp-Source: ABdhPJxf+6uLG/Y2ljHcsChPE+oY3J+gk3Kl1nNxYTtxiBfoP4oERbrxXXoZVsfQmFgE4AI8sPfu7fwDiECsZIJ+Pkw= X-Received: by 2002:a02:942a:: with SMTP id a39mr17381196jai.50.1590370991729; Sun, 24 May 2020 18:43:11 -0700 (PDT) MIME-Version: 1.0 References: <20200508145624.1.I4d7421c6bbb1f83ea58419082481082e19097841@changeid> <20200513122012.v3.1.I4d7421c6bbb1f83ea58419082481082e19097841@changeid> <87a71y93lr.fsf@linux.intel.com> In-Reply-To: <87a71y93lr.fsf@linux.intel.com> From: "Anand K. Mistry" Date: Mon, 25 May 2020 11:43:00 +1000 Message-ID: Subject: Re: [PATCH v3] perf record: Use an eventfd to wakeup when done To: Andi Kleen Cc: linux-perf-users@vger.kernel.org, Alexander Shishkin , Arnaldo Carvalho de Melo , Ingo Molnar , Jiri Olsa , Mark Rutland , Namhyung Kim , Peter Zijlstra , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 23 May 2020 at 23:35, Andi Kleen wrote: > > Anand K Mistry writes: > > } > > > > + done_fd = eventfd(0, EFD_NONBLOCK); > > This will make perf depend on a recent glibc or other library > that implements eventfd. Wouldn't surprise me if some kind > of build time check is needed for this to pass all of Arnaldo's > built tests. Looks like Arnaldo made that change when merging: https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/commit/?h=perf/core&id=e9db221d37f91409040cf7f3fbed08b44e055ae9 This makes me curious. How old a kernel should modern tools support? >From the man page, eventfd was added in 2.6.22 (and eventfd2 in 2.6.27), which was 2007 (or 2008 for eventfd2) and glibc-2.8 which was 2008. I understand the kernel's policy of never breaking userspace, but what about userspace tools? > > > -Andi -- Anand K. Mistry Software Engineer Google Australia