From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dario Faggioli Subject: Re: [PATCH 06/14] xen: sched: tracing: enable TSC tracing for all events Date: Mon, 15 Feb 2016 18:00:18 +0100 Message-ID: <1455555618.14334.74.camel@citrix.com> References: <20160205183137.4543.56523.stgit@Solace.station> <20160205183418.4543.5548.stgit@Solace.station> <20160215163212.GF4697@char.us.oracle.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============7621429374268951198==" Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1aVMVd-0007aB-CI for xen-devel@lists.xenproject.org; Mon, 15 Feb 2016 17:00:25 +0000 In-Reply-To: <20160215163212.GF4697@char.us.oracle.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Konrad Rzeszutek Wilk Cc: xen-devel@lists.xenproject.org, Olaf Hering , Tianyang Chen , Meng Xu , George Dunlap List-Id: xen-devel@lists.xenproject.org --===============7621429374268951198== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-ov9ei3ECOOSDmtZo0JNC" --=-ov9ei3ECOOSDmtZo0JNC Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, 2016-02-15 at 11:32 -0500, Konrad Rzeszutek Wilk wrote: > On Fri, Feb 05, 2016 at 07:34:18PM +0100, Dario Faggioli wrote: > > it is enabled for pretty much all of them already. > > There were just a few that had it disabled. > >=20 > > When tracing a scheduler, timing information is > > really important, so enable it everywhere scheduling > > related. > >=20 > > Note that this was not really a problem if looking > > at the traces with xenalyze, but it was if using > > xentrace_format. >=20 > Was there any historical reason it was not used? >=20 I don't really know. Funnily enough, for Credit1, it looks like it was me that did it in=C2=A0cbcbe82f "xen: sched_credit: add some tracing". At the time, Credit= 2 had some tracing already, and the TRC_CSCHED2_TICKLE was not logging the TSC. The only reason I could think of is that, when doing TRC_CSCHED_TICKLE, I "took inspiration" from what I found already in the code base (yeah, I know, bad me! :-/). As per why Credit2 does that in the first place, this is when it started:=C2=A01b561702 "credit2: Fix runq_tickle to use idle, tickled masks", from George. In that commit,=C2=A0TRC_CSCHED2_TICKLE_CHECK is moved and, while doing so, it looses the "TSC logging" property, while TRC_CSCHED2_TICKLE is introduced from scratch, and that's directly with log_tsc=3D0. I can't tell why that is the case, and I think we should change that. As said in the commit message, xenalyze does not have much problems with all this, so it's certainly not a super big deal (and it may even be the reason why this went unnoticed until now, I guess). However, if looking at the output of xentrace_format (which is a lot less smart than xenalyze!) it indeed is quite useful to see the timestamp (not to mention that, without it, the output itself is rather disturbing to look at and post-process, for severe lack of alignment). Maybe George knows better, but in any case, I think we should turn this on. :-) Thanks and Regards, Dario --=20 <> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) --=-ov9ei3ECOOSDmtZo0JNC Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEABECAAYFAlbCBCIACgkQk4XaBE3IOsROOACffwwIS3TsNpa428JxY0J8FR2o v88An3SGc82YAbkIiU7pVRwzV0a0eOK6 =dvyt -----END PGP SIGNATURE----- --=-ov9ei3ECOOSDmtZo0JNC-- --===============7621429374268951198== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel --===============7621429374268951198==--