From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dario Faggioli Subject: Re: xen 4.5.0 rtds scheduler perform poorly with 2vms Date: Sun, 29 Nov 2015 17:27:09 +0100 Message-ID: <1448814429.7833.303.camel@citrix.com> References: <1448410554.7833.119.camel@citrix.com> <1448644982.7833.290.camel@citrix.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============2369682581003178770==" Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Meng Xu , "Yu-An(Victor) Chen" Cc: "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org --===============2369682581003178770== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-FsxkDUztSZfYpvuPn3/7" --=-FsxkDUztSZfYpvuPn3/7 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sun, 2015-11-29 at 10:38 -0500, Meng Xu wrote: >=20 >=20 > 2015-11-29 7:46 GMT-05:00 Yu-An(Victor) Chen : > > Hi Meng, > >=20 > Hi,=C2=A0 > =C2=A0 > >=20 > > So I will rewrite my setup here again, but this time I shorten the > > period and budget for RTDS like you suggested: > >=20 > Nice! :-) >=20 > =C2=A0 > > ----------------------------------------------------------------- > > ------------------------------------------------------------ > >=20 > (I like this line, BTW. :-D)=C2=A0 > >=20 > >=20 > > for xen-credit : 2vms (both vm are given 8 vCPUs) sharing 8 cores > > (cpu 0-7) using credit scheduler(both with weight of 800 and > > capacity of 400) > > for xen-rtds: 2 vms (both vm are given 8 vCPUs) sharing 8 cores > > (cpu0-7) using RTDS (both with period of 4000(4ms) and budget of > > 2000(2ms)))=20 > > In both setup, dom0 is using 1 core from cpu 8-15 > >=20 > > In both setup: > >=20 > > I loaded VM2 with constant running task with total utilization of 4 > > cores. > > and in VM1 I run iterations of tasks of total utilization rate of 1 > > cores, 2 cores, 3 cores, 4 cores, and then record their > > schedulbility. > > ----------------------------------------------------------------- > > ------------------------------------------------------------ > >=20 > > So st_jobs_stats for the missed deadline jobs are: > >=20 > > trial #1 composed of 2 tasks: total tasks utilization rate =3D 1 > >=20 > > (period, exe, deadline)=3D(21ms,12.023ms,21ms) -> miss all deadline > > (period, exe, deadline)=3D(100ms,37.985ms,100ms) -> no miss > >=20 > yes, this is the information I need and we can solve the mystery > now...=C2=A0 > Let's look at this task: > (period, exe, deadline)=3D(21ms,12.023ms,21ms) -> miss all deadline > Its utilization is 12.023 / 21 ~=3D 0.5614; > Your VCPU utilization is only 2ms / 4ms =3D 0.5=C2=A0 > So even when this task is pinned to one VCPU, it will still miss > deadline because it has only one thread. :-) > Mmmm... As I said many times, I don't remember much of all those RT schedulability formulas, but, is really that simple? I mean, if the in- guest scheduling algorithm is global (e.g., global-EDF), the task could migrate, couldn't it? Is it really the case that you can never schedule tasks with U greater than the smaller U of the various vCPUs (which seems to me to be what you're implying)? Anyway... > So basically, it is because your configuration is incorrect. That's > also why you need to read some literatures in real-time scheduling > theory. ;-)=20 >=20 ... I totally agree with this! ;-D Regards, Dario > =C2=A0 --=20 <> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) --=-FsxkDUztSZfYpvuPn3/7 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 iEYEABECAAYFAlZbJ10ACgkQk4XaBE3IOsSXWQCeKlalAfcKIa+F/k5fIRzCXvRd KIUAnRDJI9lFvxiDvBRS6Hu12UwYh0rj =HjRO -----END PGP SIGNATURE----- --=-FsxkDUztSZfYpvuPn3/7-- --===============2369682581003178770== 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 --===============2369682581003178770==--