Date: Wed, 25 Jul 2018 09:19:12 +1000 From: Jason Tubnor <jason@tubnor.net> To: Shawn Webb <shawn.webb@hardenedbsd.org> Cc: Alan Somers <asomers@freebsd.org>, "freebsd-virtualization@freebsd.org" <virtualization@freebsd.org> Subject: Re: Overcommitting CPUs with BHyve? Message-ID: <CACLnyCKSuVo04cvfnAYdu6r5R00rrvD8SPkS4DNBXERutYAo4Q@mail.gmail.com> In-Reply-To: <20180724221230.tcljojufbwdl5ywy@mutt-hbsd> References: <CAOtMX2hEPnBaaKk25YWe6mYW-gCA6pGssEHTBB4GJ-C6sQU%2Btg@mail.gmail.com> <20180724221230.tcljojufbwdl5ywy@mutt-hbsd>
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On Wed, 25 Jul 2018 at 08:12, Shawn Webb <shawn.webb@hardenedbsd.org> wrote: > On Tue, Jul 24, 2018 at 03:30:32PM -0600, Alan Somers wrote: > > What are people's experiences with overcommitting CPUs in BHyve? I have > an > > 8-core machine that often runs VMs totalling up to 5 allocated CPUs > without > > problems. But today I got greedy. I assigned 8 cores to one VM for a > big > > build job. Obviously, some of those were shared with the host. I also > > assigned it 8GB of RAM (out of 16 total). Build performance fell through > > the floor, even though the host was idle. Eventually I killed the build > > and restarted it with a more modest 2 make jobs (but the VM still had 8 > > cores). Performance improved. But eventually the system seemed to be > > mostly hung, while I had a build job running on the host as well as in > the > > VM. I killed both build jobs, which resolved the hung processes. Then I > > restarted the host's build alone, and my system completely hung, with > > top(1) indicating that many processes were in the pfault state. > > > > So my questions are: > > 1) Is it a known problem to overcommit CPUs with BHyve? > > 2) Could this be related to the pfault hang, even though the guest was > idle > > at the time? > 1) Not that I have experienced. 2) More likely RAM pressure. Are you running ZFS? What is you ARC capped at? (Total guest + System + ARC < System Total Ram) > VMWare's ESXi uses a special scheduler to do what it does. I wonder if > it would be worthwhile to investigate implementing a scheduler in > FreeBSD that provides decent performance for virtualized workloads. > > >
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