Fix rate option with iodepth > 1
The rate option currently doesnt work when used with libaio engine.
The math currently, calculates the time t2 (when the I/O completed) -
t1 (when the io_u unit was created) as the time it takes for the I/O
and the bandwidth for the rate calculation is calculated from that.
This math will work correctly for sync engine as there is only one io
in progress at a time, but for libaio engine, when there are multiple
I/Os queued, the same time (as in from t1 to t2) could be attributed
to other I/Os as well so the actual bandwidth is actually higher.
I have a patch, but this is more brute force where I take the total
bytes read/written divided by the time since I/Os started to calculate
the bandwidth and decide on the time that needs to be spent sleeping
(if any).This is a little more heavy weight than the previous math. I
think there are probably simpler/cleaner solutions than this but this
is the current patch I have for it.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.h b/fio.h
index 3b2dd6e..119dc09 100644
--- a/fio.h
+++ b/fio.h
@@ -359,7 +359,7 @@
/*
* Rate state
*/
- unsigned long rate_usec_cycle[2];
+ unsigned long rate_nsec_cycle[2];
long rate_pending_usleep[2];
unsigned long rate_bytes[2];
unsigned long rate_blocks[2];