Howdie all,
we recently upgraded our OpenSuse to 12.1 from 11.2 and since then have troubles with disk io on our server. The problem is that
one process (progress database restore of multi GB DB hogs all disk io and starves others. For example mysqld. We see latencys on
fsync for mysqld of 15s + with cfq block io scheduler. Still 5s+ with deadline block io scheduler and read_expire reduced to 20ms.
Been unable to reduce latency for other processes any further.
Our guess to the culprit is that the improvment that was made in 2.6.37 for smp ext4 block io throuput (300-400% according to
Linux 2 6 37 - Linux Kernel Newbies ) has made it possible for one process to be that fast and created this starvation problem.
Or maybe some kernel bug.
Anybody have any pointers about how to reign in disk-io hogs in 3.1?
best regards
remosito
PS Some info about the Server: Dell T710 with 2 Xeon 6 core procs, 48GB Memory. 6x300GB Disks in RAID10 on a H700 Raid Controller.
We didn’t mess with many default Suse Kernel values. Except swapiness, default blocksize of Tape Driver, Max Semaphore and Shared Memory Segment
Values (cat /proc/sys/kernel/shmmax shmmni shmall). And of course the ioscheduler as deadline scheduler makes the system less unusable…
