Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760108Ab3IDUjl (ORCPT ); Wed, 4 Sep 2013 16:39:41 -0400 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:35754 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753562Ab3IDUjj (ORCPT ); Wed, 4 Sep 2013 16:39:39 -0400 Message-ID: <52279A81.6010008@linux.vnet.ibm.com> Date: Thu, 05 Sep 2013 02:09:29 +0530 From: Hemant User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Mark Wielaard CC: Namhyung Kim , Masami Hiramatsu , Ingo Molnar , linux-kernel@vger.kernel.org, srikar@linux.vnet.ibm.com, peterz@infradead.org, oleg@redhat.com, mingo@redhat.com, anton@redhat.com, systemtap@sourceware.org Subject: Re: [RFC PATCH 0/2] Perf support to SDT markers References: <20130903072944.4793.93584.stgit@hemant-fedora> <20130903082503.GA20732@gmail.com> <5225A937.2050507@hitachi.com> <5225E2C5.3080001@linux.vnet.ibm.com> <87a9jtt72j.fsf@sejong.aot.lge.com> <1378283148.4321.16.camel@bordewijk.wildebeest.org> <522777FF.2040906@linux.vnet.ibm.com> <1378320735.4321.62.camel@bordewijk.wildebeest.org> In-Reply-To: <1378320735.4321.62.camel@bordewijk.wildebeest.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13090420-1396-0000-0000-000003816057 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1768 Lines: 40 On 09/05/2013 12:22 AM, Mark Wielaard wrote: > On Wed, 2013-09-04 at 23:42 +0530, Hemant wrote: >> On 09/04/2013 01:55 PM, Mark Wielaard wrote: >>> Note that if you use the normal DTRACE_PROBE macros no semaphore will be >>> inserted. And you can opt to not support probes that have a semaphore in >>> perf if you think that is easier (just check the semaphore link-time >>> address for the probe, it should normally be zero). Just warn: "No way I >>> am going to probe something that might have a little extra overhead! I >>> am no debugger..." :) >> I agree. There will be an extra overhead but there may be some important >> markers (on which we need to probe) may be worth this overhead? > Yes, there maybe. And gdb and stap do support them. But it means not > just setting the probe, but also incrementing (and decrementing) the > semaphore. See "Semaphore Handling" under > https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation > > Which is extra work, so for a minimal implementation that just supports > normal (no-overhead) probes you might want to skip the extra work > required to support them. I believe they are normally not used. I > wouldn't recommend them and when I have added SDT probes myself I never > used/needed them, but I haven't actually looked what others do. Hmm, I agree as normally they aren't used. Also in normal usage, they aren't needed. Avoiding this seems the right choice for now. Will just filter out them as suggested by Masami. Thanks Hemant > > Cheers, > > Mark > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/