On Mon, 16 Apr 2012 14:39:12 -0700 Adrian Chadd <adr...@freebsd.org> wrote:
> On 11 April 2012 10:21, Gary Jennejohn <gljennj...@googlemail.com> wrote: > > > Just for the archive my bad disk performance seems to have been fixed in > > HEAD by svn commit r234074. Seems that all interrupts were being handled > > by a single CPU/core (I have 6), which resulted in abysmal interrupt > > handling when mutltiple disks were busy. > > > > Since this commit my disk preformance is back to normal and long lags > > are a thing of the past. > > Hi, > > This is kind of worrying. You only have a few disks, a single core > SHOULD be able to handle all the interrupts for those disks whilst > leaving plenty of cycles to spare to drive the rest of your system. > And you have 5 other cores. > > Would you be willing to help out diagnose exactly why that particular > behaviour is causing you so much trouble? It almost sounds like > something in the IO path is blocking for far too long, not allowing > the rest of the system to move forward. That's very worrying for an > interrupt handler. :) > Yes, I agree completely. My first thought was that disk I/O scheduling had somehow been pessimized. But then I thought - wait a minute, I have disk caches enabled and command queuing is enabled for all of them, so that shouldn't really have any noticeable impact. So I was at a loss to explain why disk performance had suddenly gotten so bad. I'd be willing to spend some time on diagnosing it, but I have to come up with a scenario which would reliably reproduce the problem. AFAICR it generally happened when I was running csup/svn because my CVS repositoy is on one disk and /usr/{ports,src} are on a different one. I still have the old problem kernel around, but it's probably not instrumented for any meaningful diagnoses. -- Gary Jennejohn _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"