Date: Tue, 23 Aug 2016 18:34:45 +1000 From: Jan Mikkelsen <janm@transactionware.com> To: Kevin Oberman <rkoberman@gmail.com> Cc: "freebsd-emulation@freebsd.org" <emulation@freebsd.org> Subject: Re: Odd behavior with virtualbox-ose-4.3.38 Message-ID: <C75C1936-ECF9-48A9-97A7-FA12A9023D2E@transactionware.com> In-Reply-To: <CAN6yY1s6%2BqdMJ5BpmkBB_3H1a8HPSvAoaS3QobcFGMHKfXq1Cw@mail.gmail.com> References: <CAN6yY1vn_o%2B=bX7MRNwnurp_G%2BDRhD3sfSS63-1hx4JbYsVaSw@mail.gmail.com> <CAN6yY1sG92DUR0-7Y_wE-r94%2B22JZszgcsOy=XrY=J77njUC_Q@mail.gmail.com> <2418C811-3C6E-4837-B6A5-51DB4C425EB4@transactionware.com> <CAN6yY1v%2BfxZKYexP5m=xUtqaoPjm1zM_4LHXtY5YD_2qAecOoQ@mail.gmail.com> <59E9F6CE-0F2B-40E1-B78D-AF9DFBCED280@transactionware.com> <CAN6yY1s=EPL-nYxDrgvgxG4xQnhVaOiODwHLy3MXX-dqpddouA@mail.gmail.com> <CAN6yY1s6%2BqdMJ5BpmkBB_3H1a8HPSvAoaS3QobcFGMHKfXq1Cw@mail.gmail.com>
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> On 23 Aug 2016, at 14:37, Kevin Oberman <rkoberman@gmail.com> wrote: >=20 > On Mon, Aug 22, 2016 at 4:30 PM, Kevin Oberman <rkoberman@gmail.com = <mailto:rkoberman@gmail.com>> wrote: > On Mon, Aug 22, 2016 at 12:54 PM, Jan Mikkelsen = <janm@transactionware.com <mailto:janm@transactionware.com>> wrote: > [ =E2=80=A6 ] > Yes, the problem could be in many places. However, if you=E2=80=99ve = gone to FreeBSD 11, you have more aio than you think. =46rom UPDATING: > 20160301: > The AIO subsystem is now a standard part of the kernel. The > VFS_AIO kernel option and aio.ko kernel module have been = removed. > Due to stability concerns, asynchronous I/O requests are only > permitted on sockets and raw disks by default. To enable > asynchronous I/O requests on all file types, set the > vfs.aio.enable_unsafe sysctl to a non-zero value. >=20 > BINGO! >=20 > Thank you so much, Jan! This does explain a great deal of what I was = seeing and why.=20 >=20 > Now the question... how can I disable it? I'm guessing that = "kern.features.aio=3D0" in /boot/loader.conf might do the trick, but the = man page does not mention this at all. Also, I guess it is time to open = a bug report on this. FWIW, the problem does seem to be linked to disk = activity. I had the system locked up and had to kill the process. When I = rebooted, the system told me that a disk check was needed, but I had it = lock up several time (3, I think) before it made it through the check = without locking up again. Once that was complete, the system started and = ran normally again. This also now fits rather well with an aio issue. >=20 > Not too sure how to go about collecting more information for the = PR,but I'll open it with what I have. >=20 > Thanks again, Jan! > -- > Kevin Oberman, Retired Network Engineer >=20 > FYI, there is a PR on this. = https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D168298 = <https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D168298>; >=20 > I have updated the ticket with what I have seen, especially that it is = not ZFS specific. I have also made the adjustment in sysctls as shown in = the ticket (comment 3) and will see how things works. Glad it was useful. Looking at the link to the 2012 email in the PR, I = see that I responded back then. At the time my workaround was to turn on = hostbuffercache in Virtualbox; obviously not enough now. The sysctls = will probably achieve something similar =E2=80=94 make it less likely = that aio calls will fail with EAGAIN. Just had a quick look at the Virtualbox source =E2=80=94 there is a = FreeBSD specific AIO implementation. It could easily have a bug or = trigger a FreeBSD bug. No one has found it because it doesn=E2=80=99t = run on other platforms and on FreeBSD everyone has been turning off AIO = for Virtualbox for years. Regards, Jan.=
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