Date: Mon, 30 Mar 2015 23:52:16 +0000 From: Andrew Daugherity <adaugherity@tamu.edu> To: =?Windows-1252?Q?Roger_Pau_Monn=E9?= <roger.pau@citrix.com> Cc: "freebsd-xen@freebsd.org" <freebsd-xen@freebsd.org> Subject: Re: Poor performance with FreeBSD 10.1 under Xen 4.2 Message-ID: <57429F3F-8CC9-4C4F-86DF-3E63C5853B01@tamu.edu> In-Reply-To: <5516A998.10206@citrix.com> References: <115BE54D-078A-4C45-8904-861DAB316C03@tamu.edu> <5516A998.10206@citrix.com>
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> On Mar 28, 2015, at 8:16 AM, Roger Pau Monn=E9 <roger.pau@citrix.com> wro= te: >=20 > Hello, >=20 > Thanks for the detailed description of the issue. I've reproduced your > benchmarks and with the hardware I've used (Core i3-5010U) I'm not able > to see this performance issue, below are the figures in my case: > [...] >=20 > I'm Ccing feld because IIRC he found something similar on one of his > boxes, that also had VTx but no EPT (just like yours). Would it be > possible for you to try the same set of tests on a different hardware? I think you're on to something. I copied this FreeBSD 10.1 VM to a system = running the same version of Xen (and same SLES in the Dom0), but with an Op= teron 2360SE CPU (which has both SVM and NPT), and it is *much* faster (and= feels more responsive too): Forked, executed and destroyed 5000 processes in 5.216613 seconds. [Subsequent runs are consistently between 5.1 and 5.5 seconds.] sssd configure: 22.210u 8.751s 0:30.39 101.8% 4915+236k 0+300io 31pf+0w sssd build: 176.556u 78.846s 2:15.77 188.1% 5534+217k 49+44io 8pf+0w I'll run some more benchmarks, but I don't recall Linux VMs being noticeabl= y different in speed between the Opteron and the Xeon systems -- I'm pretty= sure it's not a case of a raw CPU power advantage. > Also, if even FreeBSD 10.1 compiled without XENHVM shows this issue it > means there's something in the generic code that doesn't work well when > running virtualized on this specific hardware, but I'm afraid figuring > it out is not trivial. One place to start would be asking on > freebsd-hackers and freebsd-virt. I suppose this performance delta with presence of EPT/NPT vs. lack thereof = means it's time to take it to those lists? My next step will be to test 10= .1 under KVM on the Xeon to confirm whether it's a Xen issue or strictly EP= T. Thanks for the tips! -Andrew
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