From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933232AbbESOtm (ORCPT ); Tue, 19 May 2015 10:49:42 -0400 Received: from mail-pa0-f52.google.com ([209.85.220.52]:35843 "EHLO mail-pa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933088AbbESOtk (ORCPT ); Tue, 19 May 2015 10:49:40 -0400 Date: Tue, 19 May 2015 23:48:18 +0900 From: Namhyung Kim To: Adrian Hunter Cc: Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, Jiri Olsa Subject: Re: [PATCH 5/5] perf tools: Fix data_read_offset() file opening Message-ID: <20150519144818.GA29162@danjae.kornet> References: <1432040746-1755-1-git-send-email-adrian.hunter@intel.com> <1432040746-1755-6-git-send-email-adrian.hunter@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1432040746-1755-6-git-send-email-adrian.hunter@intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Adrian, On Tue, May 19, 2015 at 04:05:46PM +0300, Adrian Hunter wrote: > Patch "perf tools: Protect dso cache fd with a mutex" > changed data_file_size() to open the data file if it > was not open. > > data_read_offset() was calling data_file_size() to read > the data file size, but data_file_size() can fail to > open the file because the binary_type has not been set up. > > The correct function to call is dso__data_size() which > uses dso__data_fd() to open the file correctly. Right, but I worried about the locking overhead. By using dso__data_size() it'll call dso__data_fd() everytime which grabs the dso__data_open_lock that is a global mutex. It can be a performance bottleneck on multi-thread report IMHO. I assumed that correct code should check the data fd or size before calling read function as I read the comment in dso.h file. What about adding the missing check in a proper place instead? Thanks, Namhyung > > Signed-off-by: Adrian Hunter > --- > tools/perf/util/dso.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c > index 1b96c8d..e248f56 100644 > --- a/tools/perf/util/dso.c > +++ b/tools/perf/util/dso.c > @@ -756,7 +756,7 @@ off_t dso__data_size(struct dso *dso, struct machine *machine) > static ssize_t data_read_offset(struct dso *dso, struct machine *machine, > u64 offset, u8 *data, ssize_t size) > { > - if (data_file_size(dso, machine)) > + if (dso__data_size(dso, machine) < 0) > return -1; > > /* Check the offset sanity. */ > -- > 1.9.1 >