Date: Tue, 24 Jul 2018 19:47:47 -0400 From: Allan Jude <allanjude@freebsd.org> To: freebsd-virtualization@freebsd.org Subject: Re: Overcommitting CPUs with BHyve? Message-ID: <e86ad15d-10bb-4eb2-7de7-50716ee4642f@freebsd.org> In-Reply-To: <CAOtMX2hEPnBaaKk25YWe6mYW-gCA6pGssEHTBB4GJ-C6sQU%2Btg@mail.gmail.com> References: <CAOtMX2hEPnBaaKk25YWe6mYW-gCA6pGssEHTBB4GJ-C6sQU%2Btg@mail.gmail.com>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --ufdwLLnHSBp9FFXIXB1kcmN0LElR0gzIA Content-Type: multipart/mixed; boundary="LnBBkp24fKFRDj36YuniA37gh3QUFhj40"; protected-headers="v1" From: Allan Jude <allanjude@freebsd.org> To: freebsd-virtualization@freebsd.org Message-ID: <e86ad15d-10bb-4eb2-7de7-50716ee4642f@freebsd.org> Subject: Re: Overcommitting CPUs with BHyve? References: <CAOtMX2hEPnBaaKk25YWe6mYW-gCA6pGssEHTBB4GJ-C6sQU+tg@mail.gmail.com> In-Reply-To: <CAOtMX2hEPnBaaKk25YWe6mYW-gCA6pGssEHTBB4GJ-C6sQU+tg@mail.gmail.com> --LnBBkp24fKFRDj36YuniA37gh3QUFhj40 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 2018-07-24 17:30, Alan Somers wrote: > What are people's experiences with overcommitting CPUs in BHyve? I hav= e an > 8-core machine that often runs VMs totalling up to 5 allocated CPUs wit= hout > 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 throu= gh > the floor, even though the host was idle. Eventually I killed the buil= d > 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. >=20 > 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? >=20 > -Alan > _______________________________________________ > freebsd-virtualization@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-virtualization > To unsubscribe, send any mail to "freebsd-virtualization-unsubscribe@fr= eebsd.org" >=20 Bhyve has a command line flag, -p, to let you pin a vCPU to a physical CPU. This might avoid some of the issues with the threads hopping around all the time. If you were anyone else, I'd also ask if you ensured your vfs.zfs.arc_max was low enough to actually leave some ram for the VM to u= se. --=20 Allan Jude --LnBBkp24fKFRDj36YuniA37gh3QUFhj40-- --ufdwLLnHSBp9FFXIXB1kcmN0LElR0gzIA Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (MingW32) iQIcBAEBAgAGBQJbV7qnAAoJEBmVNT4SmAt+8fMQAJgOCZ4RdlDo0S6/La12v+Qm /TswUy8DFGtbNc0h6nDXUVPv4vjSFXUUS1mGV2dceRuqs567289EDYjK6DT0/jkd pPnhHDDWP5+kokLuLVbt34qp0vxia+5/CBcnxntFWSglH0bEzqN5wmqcpJYhUPuK 76k+soOdhvajUlBEE+UbE2cNZkFpYdgUo7WLGzh8116PJT2a+N0uIxHFbppwsSQb Vjh9M4rut/rI4gh0zxQyljbMFD/VW93AfwQ6KgE155GL+gVul2BNwX982AHlMxk5 vX1U5jUuLuatN9olEyhFhareVGM5mY8oAb8U6yUkLvn7+nN1FJcUCtsh/zsBIVAN boci1iH1IwsFCswlXk3NZbJqoON9M1z7woEXVqXQBtSsyPQ3hU1quymmTHM3Xb2d g1zBy3njmAZYUQ1DLxg0GV9j/X/1JVMOhZIR1NRyV0rFMdL3RGjH8QSXRlZrfdSR a8agfWLypqRK5dsxX2o7wx8GJa1iPRbXH6KSs5hQZpJ8izYizswRhv2inHWiWWvM B91md7GY1Olrk9B1LcyQ3ipOFvXTDKT6xrVYy2HNIPLtknSMXnab2mLnRIbqxiWo MVz0NMOIHPHVk58aaPnZikSlXViezSChJUX/HaYcuVE/0IORAoxDqIFuYdoo/+hm tWNPMUZOYzxkNnTLaIIz =9yAw -----END PGP SIGNATURE----- --ufdwLLnHSBp9FFXIXB1kcmN0LElR0gzIA--
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