From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dario Faggioli Subject: Re: [PATCH 3/9] xen: sched: make locking for {insert, remove}_vcpu consistent Date: Thu, 8 Oct 2015 22:44:37 +0200 Message-ID: <1444337077.22254.78.camel@citrix.com> References: <20150929164726.17589.96920.stgit@Solace.station> <20150929165549.17589.76223.stgit@Solace.station> <560ACAD5.8040405@citrix.com> <56168479.60703@citrix.com> <561689B6.4020306@citrix.com> <56169E00.9060902@citrix.com> <5616A6A2.2090102@citrix.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0041633999025376165==" Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1ZkI3R-0002Hg-Kt for xen-devel@lists.xenproject.org; Thu, 08 Oct 2015 20:44:45 +0000 In-Reply-To: <5616A6A2.2090102@citrix.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: Andrew Cooper , George Dunlap , xen-devel@lists.xenproject.org Cc: George Dunlap , Meng Xu List-Id: xen-devel@lists.xenproject.org --===============0041633999025376165== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-TPXIr/npgi9mLXUnlPiS" --=-TPXIr/npgi9mLXUnlPiS Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2015-10-08 at 18:23 +0100, Andrew Cooper wrote: > On 08/10/15 17:46, George Dunlap wrote: > > On 08/10/15 16:20, Andrew Cooper wrote: > > > There are a lot of codepaths, but I cant see one which is > > > definitely > > > called with interrupts disables. (OTOH, I can see several where > > > interrupts are definitely enabled). > > Oh, I think I misunderstood you. You meant, "No codepaths *calling > > into* generic scheduling code should need interrupts disabled at > > all". > > I can certainly believe that to be true in most cases; there's no > > sense > > in saving the flags if we don't need to. >=20 > My original statement came from the observation that schedule() runs > with interrupts disabled, and takes between 2.2 and 4 microseconds to > run (as measured during the ticketlock performance analysis). >=20 Ok, this part, I got, I think. BTW, do you still have the scripts/harness/whatever to perform such analysis? I'm asking because I'm about to give it a try at reducing the amount of time during which the scheduler keeps interrupt disabled. If I manage, it'd be nice to retry it, an get updated numbers. > I am going to go out on a limb and say that the majority of that time > does not need to be spent with interrupts disabled. I might easily > be > wrong, but I suspect I am not. >=20 I'll have a look and let you know what I find. Regards, Dario --=20 <> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) --=-TPXIr/npgi9mLXUnlPiS 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 iEYEABECAAYFAlYW1bUACgkQk4XaBE3IOsSzNQCgh0K8LxXF+LTybFy+/KutHrZR NawAoI5hKYuXkYVKqRrdv0hU7GM/Ed1i =oDeX -----END PGP SIGNATURE----- --=-TPXIr/npgi9mLXUnlPiS-- --===============0041633999025376165== 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 --===============0041633999025376165==--