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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 E7E2ECA9EC0 for ; Tue, 29 Oct 2019 02:14:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BD48F20679 for ; Tue, 29 Oct 2019 02:14:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730485AbfJ2COV (ORCPT ); Mon, 28 Oct 2019 22:14:21 -0400 Received: from mga02.intel.com ([134.134.136.20]:11033 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729412AbfJ2COV (ORCPT ); Mon, 28 Oct 2019 22:14:21 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Oct 2019 19:14:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,242,1569308400"; d="scan'208";a="205342149" Received: from tassilo.jf.intel.com (HELO tassilo.localdomain) ([10.7.201.137]) by FMSMGA003.fm.intel.com with ESMTP; 28 Oct 2019 19:14:20 -0700 Received: by tassilo.localdomain (Postfix, from userid 1000) id 0198C301C0F; Mon, 28 Oct 2019 19:14:19 -0700 (PDT) Date: Mon, 28 Oct 2019 19:14:19 -0700 From: Andi Kleen To: Jiri Olsa Cc: Andi Kleen , acme@kernel.org, jolsa@kernel.org, eranian@google.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 1/7] perf pmu: Use file system cache to optimize sysfs access Message-ID: <20191029021419.GT4660@tassilo.jf.intel.com> References: <20191025181417.10670-1-andi@firstfloor.org> <20191025181417.10670-2-andi@firstfloor.org> <20191028220137.GF28772@krava> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191028220137.GF28772@krava> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 28, 2019 at 11:01:37PM +0100, Jiri Olsa wrote: > On Fri, Oct 25, 2019 at 11:14:11AM -0700, Andi Kleen wrote: > > SNIP > > > if (pmu_aliases_parse(path, head)) > > return -1; > > @@ -525,7 +524,6 @@ static int pmu_alias_terms(struct perf_pmu_alias *alias, > > */ > > static int pmu_type(const char *name, __u32 *type) > > { > > - struct stat st; > > char path[PATH_MAX]; > > FILE *file; > > int ret = 0; > > @@ -537,7 +535,7 @@ static int pmu_type(const char *name, __u32 *type) > > snprintf(path, PATH_MAX, > > "%s" EVENT_SOURCE_DEVICE_PATH "%s/type", sysfs, name); > > > > - if (stat(path, &st) < 0) > > + if (access(path, R_OK) < 0) > > why not file_available call in here? iirc it doesn't do any redundant accesses. -Andi