From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=39908 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PFTbg-0005Q5-0X for qemu-devel@nongnu.org; Mon, 08 Nov 2010 10:26:05 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PFTbe-0004Hu-Cu for qemu-devel@nongnu.org; Mon, 08 Nov 2010 10:26:03 -0500 Received: from mx1.redhat.com ([209.132.183.28]:62251) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PFTbe-0004GF-63 for qemu-devel@nongnu.org; Mon, 08 Nov 2010 10:26:02 -0500 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id oA8FPw9l001190 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 8 Nov 2010 10:25:58 -0500 Received: from file.fab.redhat.com (file.fab.redhat.com [10.33.63.6]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id oA8FPu4a015779 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Mon, 8 Nov 2010 10:25:58 -0500 Received: from file.fab.redhat.com (localhost.localdomain [127.0.0.1]) by file.fab.redhat.com (8.13.1/8.13.1) with ESMTP id oA8FPu2o017690 for ; Mon, 8 Nov 2010 15:25:56 GMT Received: (from berrange@localhost) by file.fab.redhat.com (8.13.1/8.13.1/Submit) id oA8FPuEb017686 for qemu-devel@nongnu.org; Mon, 8 Nov 2010 15:25:56 GMT Date: Mon, 8 Nov 2010 15:25:56 +0000 From: "Daniel P. Berrange" Subject: Re: [Qemu-devel] [RFC] tracing: consistent usage of "disable" in "trace-events" Message-ID: <20101108152556.GU26714@redhat.com> References: <8762w7512w.fsf@ginnungagap.bsc.es> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <8762w7512w.fsf@ginnungagap.bsc.es> Content-Transfer-Encoding: quoted-printable Reply-To: "Daniel P. Berrange" List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org On Mon, Nov 08, 2010 at 03:42:15PM +0100, Llu=C3=ADs wrote: > On the current implementation, the "disable" keyword in "trace-events" > has different semantics, depending on the backend: >=20 > * nop : ignored (not a problem) > * simple : enables tracing, but sets dynamic state to disable > * ust : disables tracing (uses nop backend) > * dtrace : same as simple >=20 > Would it be possible to just use nop whenever the event is disabled in > trace-events? If you agree I can cook the patch, as it's pretty simple. I don't particularly see the point of the 'disable' keyword existing at all, unless there are performance implications for a particular trace=20 backend. For the DTrace backend I strip & ignore the disable keyword because probes that are compiled in, reduce to a inline conditional=20 check that has no serious overhead when no trace client is active. Regards, Daniel --=20 |: Red Hat, Engineering, London -o- http://people.redhat.com/berrang= e/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://deltacloud.o= rg :| |: http://autobuild.org -o- http://search.cpan.org/~danber= r/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 95= 05 :|