From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 10805 invoked by alias); 4 Sep 2013 18:08:33 -0000 Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org Received: (qmail 10791 invoked by uid 89); 4 Sep 2013 18:08:32 -0000 Received: from e23smtp05.au.ibm.com (HELO e23smtp05.au.ibm.com) (202.81.31.147) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-SHA encrypted) ESMTPS; Wed, 04 Sep 2013 18:08:32 +0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-5.8 required=5.0 tests=BAYES_00,KHOP_THREADED,RCVD_VIA_APNIC,RP_MATCHES_RCVD autolearn=ham version=3.3.2 X-HELO: e23smtp05.au.ibm.com Received: from /spool/local by e23smtp05.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 5 Sep 2013 04:01:03 +1000 Received: from d23dlp01.au.ibm.com (202.81.31.203) by e23smtp05.au.ibm.com (202.81.31.211) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Thu, 5 Sep 2013 04:01:02 +1000 Received: from d23relay03.au.ibm.com (d23relay03.au.ibm.com [9.190.235.21]) by d23dlp01.au.ibm.com (Postfix) with ESMTP id 875BB2CE804D for ; Thu, 5 Sep 2013 04:08:26 +1000 (EST) Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r84I8FJF9830794 for ; Thu, 5 Sep 2013 04:08:15 +1000 Received: from d23av02.au.ibm.com (localhost [127.0.0.1]) by d23av02.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id r84I8PQG019023 for ; Thu, 5 Sep 2013 04:08:26 +1000 Received: from localhost.localdomain ([9.77.214.58]) by d23av02.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVin) with ESMTP id r84I8EwX018869; Thu, 5 Sep 2013 04:08:22 +1000 Message-ID: <5227770E.3060106@linux.vnet.ibm.com> Date: Wed, 04 Sep 2013 18:08:00 -0000 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: Masami Hiramatsu CC: Mark Wielaard , Namhyung Kim , 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> <5226F1B6.3000801@hitachi.com> In-Reply-To: <5226F1B6.3000801@hitachi.com> 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: 13090418-1396-0000-0000-0000038149D5 X-SW-Source: 2013-q3/txt/msg00247.txt.bz2 On 09/04/2013 02:09 PM, Masami Hiramatsu wrote: > (2013/09/04 17:25), Mark Wielaard wrote: >> On Wed, 2013-09-04 at 15:49 +0900, Namhyung Kim wrote: >>> On Tue, 03 Sep 2013 18:53:17 +0530, Hemant wrote: >>>> On 09/03/2013 02:47 PM, Masami Hiramatsu wrote: >>>>> Indeed, and also I'd like to know what versions of SDT this support, >>>>> and where we can see the technical document of that. As far as I know, >>>>> the previous(?) SDT implementation also involves ugly semaphores. >>>>> Have that already gone? >>> It seems it's not. I see the SDT v3 document still mentions semaphores. >> It mentions them, but should normally not be used. They are there for >> dtrace (source) compatibility. And you don't have to use them. >> >> Since normally a SDT probe marker is just a NOP it doesn't have any >> overhead. But if you want to add complicated arguments that you would >> normally not generate in your code, then you might want to add a >> semaphore. That way you can have probes with a bit more overhead that >> still have zero overhead when not being probed. >> >> 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..." :) > OK, I see. And in that case, we'd better filter out the markers which > use a semaphore when list it up, since we can not enable it. > > Thank you, > > But isn't it a better idea to handle semaphores, because there can be many important markers using semaphores and people may still want to probe on them? Thanks Hemant