On Sun, Nov 7, 2010 at 4:07 PM, Hermann Himmelbauer <dusty@xxxxxxx> wrote: > Am Samstag 06 November 2010 20:58:12 schrieb Stefan Hajnoczi: >> On Fri, Nov 5, 2010 at 5:16 PM, Hermann Himmelbauer <dusty@xxxxxxx> wrote: >> > I experience strange disk I/O stucks on my Linux Host + Guest with KVM, >> > which make the system (especially the guests) almost unusable. These >> > stucks come periodically, e.g. every 2 to 10 seconds and last between 3 >> > and sometimes over 120 seconds, which trigger kernel messages like this >> > (on host and/or guest): >> > >> > INFO: task postgres:2195 blocked for more than 120 seconds >> >> The fact that this happens on the host too suggests there's an issue >> with the host software/hardware and the VM is triggering it but not >> the root cause. >> >> Does dmesg display any other suspicious messages? > > No, there's anything that can be seen via dmesg. I at first suspected the > hardware, too. I can think of the following reasons: > > 1) Broken SATA cable / Harddisks - I changed some cables, no change, thus this > is probably ruled out. I also can't see anything via S.M.A.R.T. Moreover, the > problem is not bound to a specific device, instead it happens on sda - sdd, > so I doubt it's harddisk related. > > 2) Broken Power Supply / Insufficient Power - I'd expect either a complete > crash or some error messages in this case, so I'd rather rule that out. > > 3) Broken SATA-Controller - I cannot think of any way to check that, but I'd > also expect some crashes or kernel messages. I flashed the board to the > latest BIOS version, no change either. > > However, it seems no one except me seems to have this problem, so I'll buy a > new, similar but different mainboard (Intel instead of Asus), hopefully this > solves the problem. > > What do you think, any better idea? If you have the time, you can use perf probes to trace I/O requests in the host kernel. Perhaps completion interrupts are being dropped. You may wish to start by tracing requests issued and completed by the SATA driver. Stefan -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
