On Tue, 1 Jul 2014 13:19:10 -0700 "Patrick J. LoPresti" <[email protected]> wrote:
> On Tue, Jul 1, 2014 at 11:29 AM, Andras Horvath <[email protected]> wrote: > > > > I restarted copying again, and in a minute the CPU hung again with 100% I/O > > wait. The "iotop" output shows absolutely nothing, as if there was no load > > on the disks at all. Interrupt and context switch is around 20-50, so > > almost nothing (dstat output). Disk operation is zero. Load is at 5.01. The > > rsync processes that I'm using for the copy cannot be killed or force > > killed. > > How much RAM does your system have? What does "/sbin/sysctl -a | grep > vm.dirty" say? 3 GB. # /sbin/sysctl -a | grep vm.dirty vm.dirty_background_ratio = 10 vm.dirty_background_bytes = 0 vm.dirty_ratio = 20 vm.dirty_bytes = 0 vm.dirty_writeback_centisecs = 500 vm.dirty_expire_centisecs = 3000 > On machines with lots of RAM, I have seen disk subsystems act a bit > squirrelly when Linux decides to buffer (say) a few gigabytes of > writes. The traditional "vm.dirty_background_ratio" and > "vm.dirty_ratio" settings are a percentage of RAM, which gives > ludicrous behavior on modern big-memory boxes. > > Something like this is more sane: > > sysctl -w vm.dirty_background_bytes=67108864 > sysctl -w vm.dirty_background_bytes=134217728 > > This is not terribly likely to help, but it is worth a shot. If the > problem really is the disk spinning down, at least this will be more > likely to keep it busy... > > - Pat Tested it, didn't work unfortunately. Now my CPU is in 50% idle and 50% wait (dstat output). it's 2 cores, so it means 1 core is in 100% wait. Weird.
