From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932549AbcGEA0s (ORCPT ); Mon, 4 Jul 2016 20:26:48 -0400 Received: from mail.kernel.org ([198.145.29.136]:39348 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751562AbcGEA0p (ORCPT ); Mon, 4 Jul 2016 20:26:45 -0400 Date: Mon, 4 Jul 2016 21:26:41 -0300 From: Arnaldo Carvalho de Melo To: Chris Phlipot Cc: Arnaldo Carvalho de Melo , peterz@infradead.org, mingo@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/4] perf tool: Fix build when sysconf doesn't support cache line size Message-ID: <20160705002641.GA5324@kernel.org> References: <1467349955-1135-1-git-send-email-cphlipot0@gmail.com> <1467349955-1135-4-git-send-email-cphlipot0@gmail.com> <20160704224832.GZ5324@kernel.org> <577AFD08.7090303@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <577AFD08.7090303@gmail.com> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.6.1 (2016-04-27) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Mon, Jul 04, 2016 at 05:19:20PM -0700, Chris Phlipot escreveu: > > > On 07/04/2016 03:48 PM, Arnaldo Carvalho de Melo wrote: > > Em Thu, Jun 30, 2016 at 10:12:34PM -0700, Chris Phlipot escreveu: > > > Enable perf to build on libc implementations where sysconf() doesn't > > > support _SC_LEVEL1_DCACHE_LINESIZE as a parameter. > > > > > > For example, the Bionic implementation does not support this as a > > > paremter. Older versions of Bionic will throw an error when this is passed > > > in as a parameter, and more recent versions will just return 0 as the > > > cache line size. > > > > > > Signed-off-by: Chris Phlipot > > > --- > > > tools/perf/perf.c | 4 ++++ > > > 1 file changed, 4 insertions(+) > > > > > > diff --git a/tools/perf/perf.c b/tools/perf/perf.c > > > index 8f21922..113ca5b 100644 > > > --- a/tools/perf/perf.c > > > +++ b/tools/perf/perf.c > > > @@ -509,7 +509,11 @@ int main(int argc, const char **argv) > > > > > > /* The page_size is placed in util object. */ > > > page_size = sysconf(_SC_PAGE_SIZE); > > > +#ifdef _SC_LEVEL1_DCACHE_LINESIZE > > > cacheline_size = sysconf(_SC_LEVEL1_DCACHE_LINESIZE); > > > +#else > > > + cacheline_size = 0; > > > +#endif > > > > Couldn't we instead fallback to: > > > > sysfs__read_int("devices/system/cpu/cpu0/cache/index0/coherency_line_size", &cacheline_size) > > > > ? > > I agree that in general this would be a better fallback, but in all Android > images I have tested so far, "devices/system/cpu/cpu0/cache" does not exist. > I know not know of a good way to retrieve cache line size in this case. > > I would be ok with attempting to get cacheline size using using the > following methods, unless you have other ideas: > > 1. attempt to use sysconf(_SC_LEVEL1_DCACHE_LINESIZE) > 2. attempt to use > sysfs__read_int("devices/system/cpu/cpu0/cache/index0/coherency_line_size", > &cacheline_size) > 3. set to zero if both of the above fail. Ok, but perhaps we should have some sort of warning in places using this? - Arnaldo > > > > > > if (sysctl__read_int("kernel/perf_event_max_stack", &value) == 0) > > > sysctl_perf_event_max_stack = value; > > > -- > > > 2.7.4