Date: Fri, 30 Oct 2009 15:50:53 -0200 From: Danilo Baio <danilobaio@gmail.com> To: freebsd-xen@freebsd.org Subject: Re: SCHED_ULE vs SCHED_4BSD for XENHVM domU Message-ID: <5b9854910910301050j3d6d3ab8h5e9b35227b58304@mail.gmail.com> In-Reply-To: <C83E1FA5-EFF0-49A7-AF53-49F923948DEF@ossafe.org> References: <C83E1FA5-EFF0-49A7-AF53-49F923948DEF@ossafe.org>
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--0015174795725c964604772aab8a Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On Thu, Oct 29, 2009 at 9:12 PM, Carsten Heesch <carsten@ossafe.org> wrote: > Hi guys, > > After FreeBSD 8.0-RC2 is working well (for me) on Xen 3.3.1, I somehow ma= de > an interesting observation: > > Even if the FreeBSD domU does absolutely nothing, each of the assigned > vCPUs will be reported by xentop as using 15%-25% CPU time. It doesn't > matter, if domU is running with 1 or 4 vCPUs. All of them float at the sa= me > level. > > On the same Xen box five other domU's (CentOS 5.2-5.4) have an idle CPU > percentage of 0 to 0.5%. > > So I played a bit and figured out that changing the scheduler in the XENH= VM > kernel configuration from "option SCHED_ULE" to "option SCHED_4BSD" resol= ves > this problem. The idle state of the FreeBSD domU is now identical to the > CentOS domU's. > > However, this of course means using an old (maybe even deprecated?) > scheduler, which moreover isn't the best choice for multiple (virtual) > CPUs. > > The configuration I tested on is: > Intel i7 920 Quad-Core with Hyperthreading (8 logical CPUs) > Citrix XenServer 5.5 (based on CentOS 5.2, Xen 3.3.1) > > > Any thoughts, ideas, solutions? > > > Thanks! > > Carsten > > Hi, Same thing here. I've build 8.0-RC2 amd64 with kernel XENHVM for testing with a XenServer 5.0.0 that i have here. Only the memory information don't appear on the console of xencenter. And the processor 14% of use all the time. After build with SCHED_4BSD, 3% usage CPU. AMD64 - XENHVM freeba8# uname -a FreeBSD freeba8.localdomain 8.0-RC2 FreeBSD 8.0-RC2 #0: Fri Oct 30 15:18:43 BRST 2009 root@freeba8.localdomain:/usr/obj/usr/src/sys/XENHVM amd64 XenServer 5.0.0 (CentOS) Xen 3.2 Regards. --=20 Danilo Gon=E7alves Baio (dbaio) danilobaio (*) gmail . com +55 (44) 8801 1257 --0015174795725c964604772aab8a--
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