Comment 83 for bug 620074

Most of them look as expected, up to about 1 second latency for a single IO under load. latencytop-ext4-2*bzip2.txt looks pretty bad, though. It has a 10 second wait on a single lock_page(), that's pretty slow.

Again, this whole thread confuses me. The IO latencies from the fio jobs posted look OK, in the sense that they haven't regressed and that you can't expect zero latency when you are fully loading a disk with writes. So while we could do better there, it's not a catastrophy.

The bisect you originally did pointed to something interesting, I think. If we have clock problems, the CPU scheduler could easily delay a single process for large amounts of time if other processes are repeatedly ready to run.