From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:47484)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <cota@braap.org>) id 1fq5dJ-0004eO-UF
	for qemu-devel@nongnu.org; Wed, 15 Aug 2018 19:55:22 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <cota@braap.org>) id 1fq5dF-0004OB-T2
	for qemu-devel@nongnu.org; Wed, 15 Aug 2018 19:55:21 -0400
Received: from out1-smtp.messagingengine.com ([66.111.4.25]:50181)
	by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32)
	(Exim 4.71) (envelope-from <cota@braap.org>) id 1fq5dF-0004MZ-MP
	for qemu-devel@nongnu.org; Wed, 15 Aug 2018 19:55:17 -0400
Date: Wed, 15 Aug 2018 19:55:14 -0400
From: "Emilio G. Cota" <cota@braap.org>
Message-ID: <20180815235514.GA23767@flamenco>
References: <20180813171132.21939-1-cota@braap.org>
	<20180813171132.21939-2-cota@braap.org>
	<20180815030942.GA14092@lemon.usersys.redhat.com>
	<20180815045323.GA7585@flamenco>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20180815045323.GA7585@flamenco>
Subject: Re: [Qemu-devel] [PATCH 1/3] qsp: QEMU's Synchronization Profiler
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel/>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Fam Zheng <famz@redhat.com>
Cc: qemu-devel@nongnu.org, Peter Crosthwaite <crosthwaite.peter@gmail.com>, Stefan Weil <sw@weilnetz.de>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>, Peter Xu <peterx@redhat.com>, Markus Armbruster <armbru@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net>

On Wed, Aug 15, 2018 at 00:53:23 -0400, Emilio G. Cota wrote:
> On Wed, Aug 15, 2018 at 11:09:42 +0800, Fam Zheng wrote:
> > On Mon, 08/13 13:11, Emilio G. Cota wrote:
> > > +  --enable-sync-profiler) sync_profiler="yes"
> > > +  ;;
> > 
> > Curious, not asking for a change: can this be made a runtime option instead of
> > compile time, since there's no library dependencies? That should make this
> > somewhat easier to use.
> 
> Good point. I'll do some profiling tomorrow to see how the latency
> of the locking primitives could be minimized (ideally, not using
> the profiler should just add a well-predicted branch).

I reduced it to just a branch, but still, I measured a few percentage
points (1-2%, depending on the machine) slowdown when this is a
run-time option. (This is for a bootup+shutdown test of a guest.)

So I'll keep it as a build-time option, then.

Thanks,

		Emilio