> On 23 Aug 2016, at 14:37, Kevin Oberman <[email protected]> wrote: > > On Mon, Aug 22, 2016 at 4:30 PM, Kevin Oberman <[email protected] > <mailto:[email protected]>> wrote: > On Mon, Aug 22, 2016 at 12:54 PM, Jan Mikkelsen <[email protected] > <mailto:[email protected]>> wrote: > [ … ] > Yes, the problem could be in many places. However, if you’ve gone to FreeBSD > 11, you have more aio than you think. From 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.
> > BINGO! > > Thank you so much, Jan! This does explain a great deal of what I was seeing > and why. > > Now the question... how can I disable it? I'm guessing that > "kern.features.aio=0" 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. > > Not too sure how to go about collecting more information for the PR,but I'll > open it with what I have. > > Thanks again, Jan! > -- > Kevin Oberman, Retired Network Engineer > > FYI, there is a PR on this. > https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=168298 > <https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=168298> > > 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 — make it less likely that aio calls will fail with EAGAIN. Just had a quick look at the Virtualbox source — 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’t run on other platforms and on FreeBSD everyone has been turning off AIO for Virtualbox for years. Regards, Jan. _______________________________________________ [email protected] mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-emulation To unsubscribe, send any mail to "[email protected]"
