From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 13824 invoked by alias); 4 Sep 2013 18:12:35 -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 13816 invoked by uid 89); 4 Sep 2013 18:12:35 -0000 Received: from e23smtp07.au.ibm.com (HELO e23smtp07.au.ibm.com) (202.81.31.140) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-SHA encrypted) ESMTPS; Wed, 04 Sep 2013 18:12:35 +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: e23smtp07.au.ibm.com Received: from /spool/local by e23smtp07.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 5 Sep 2013 03:58:33 +1000 Received: from d23dlp03.au.ibm.com (202.81.31.214) by e23smtp07.au.ibm.com (202.81.31.204) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Thu, 5 Sep 2013 03:58:31 +1000 Received: from d23relay05.au.ibm.com (d23relay05.au.ibm.com [9.190.235.152]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id A73C6357804E for ; Thu, 5 Sep 2013 04:12:27 +1000 (EST) Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay05.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r84Hu3dg10551630 for ; Thu, 5 Sep 2013 03:56:03 +1000 Received: from d23av04.au.ibm.com (loopback [127.0.0.1]) by d23av04.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r84ICQWh002685 for ; Thu, 5 Sep 2013 04:12:27 +1000 Received: from localhost.localdomain ([9.77.214.58]) by d23av04.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id r84ICFRU002527; Thu, 5 Sep 2013 04:12:23 +1000 Message-ID: <522777FF.2040906@linux.vnet.ibm.com> Date: Wed, 04 Sep 2013 18:12:00 -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: 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> In-Reply-To: <1378283148.4321.16.camel@bordewijk.wildebeest.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13090417-0260-0000-0000-000003924927 X-SW-Source: 2013-q3/txt/msg00248.txt.bz2 On 09/04/2013 01:55 PM, 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..." :) 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? Thanks Hemant > >>> This link shows an example of marker probing with Systemtap: >>> https://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps >> I think the link below would be more helpful for us :) >> >> http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation > Yes, that should be the canonical description. > > Cheers, > > Mark >