Date: Fri, 23 Nov 2012 15:20:07 +0100 From: =?ISO-8859-1?Q?Bernhard_Fr=F6hlich?= <decke@FreeBSD.org> To: Alex Chistyakov <alexclear@gmail.com> Cc: "freebsd-emulation@freebsd.org" <freebsd-emulation@freebsd.org> Subject: Re: VirtualBox 4.2.4 on FreeBSD 9.1-PRERELEASE problem: VMs behave very different when pinned to different cores Message-ID: <CAE-m3X1UPsy%2Bwbqm_02JpXMr-UO3m7N6z_ZwY2HNo4GL0YUi1w@mail.gmail.com> In-Reply-To: <CA%2Bkq2xvh3j5CM7UzRVfXCeLhHwpTY%2B_M7dCJx0c27NtV8EVJwg@mail.gmail.com> References: <CA%2Bkq2xvh3j5CM7UzRVfXCeLhHwpTY%2B_M7dCJx0c27NtV8EVJwg@mail.gmail.com>
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On Fri, Nov 23, 2012 at 2:15 PM, Alex Chistyakov <alexclear@gmail.com> wrote: > Hello, > > I am back with another problem. As I discovered previously setting a > CPU affinity explicitly helps to get decent performance on guests, but > the problem is that guest performance is very different on core #0 and > cores #5 or #7. Basically when I use 'cpuset -l 0 VBoxHeadless -s > "Name" -v on' to start the VM it is barely usable at all. The best > performance results are on cores #4 and #5 (I believe they are the > same physical core due to HT). #7 and #8 are twice as slow as #5, #0 > and #1 are the slowest and other cores lay in the middle. > If I disable a tickless kernel on the guest running on #4 or #5 it > becomes as slow as a guest running on #7 so I suspect this is a > timer-related issue. > I also discovered that there are quite a lot of system interrupts on > slow guests (%si is about 10-15) but Munin does not render them on its > CPU graphs for some reason. > All my VMs are on cores #4 and #5 right now but I want to utilize > other cores too. I am not sure what to do next, this looks like a > VirtualBox bug. What can be done to solve this? I do not want to sound ignorant but what do you expect? Each VBox VM consists of somewhere around 15 threads and some of them are the vCPUs. You bind them all to the same CPU so they will fight for CPU time on that single core and latency will get unpredictable as well as performance. And then you add more and more craziness by running it on cpu0 and a HT enabled CPU ... -- Bernhard Froehlich http://www.bluelife.at/
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