IOSTAT double counting AIO write operations?
[I originally posted this in Linux-Server, but having reviewed the iostat sources it seems possible that it belongs here instead]
As part of debugging an IO generator, I've run across an odd set of results under RH 6.4 running on x64 hardware (validated on multiple systems):
-- The application uses async IO to access raw disk partitions (/dev/sdb1), and is run as root
-- The application reports 100 io/s, and 60% writes.
-- strace of the application reports 100 calls per second to io_submit() and io_getevents(), reflecting 100 AIO operations per second
-- 'dstat --aio' shows 100 ops per second
-- iostat reports 40 reads/sec, as expected, but 120 writes/second, twice as many as expected
Have you seen this behavior? Is it a known bug?