On 04/24/2015 11:10 AM, Mansour Shafaei Moghaddam wrote:
But I still think that the time is not relative to anything except the
beginning of the job i.e., 0:00:00. I again tried running the
following trace:
io version 2 iolog
/dev/sde add
/dev/sde open
/dev/sde read 1499999997952 16384
/dev/sde read 4499992682496 16384
/dev/sde read 4499992682496 16384
/dev/sde wait 3000 16384
/dev/sde read 4499992682496 16384
/dev/sde read 4499992682496 16384
/dev/sde read 4499992682496 16384
/dev/sde wait 5000 16384
/dev/sde read 1499999997952 16384
/dev/sde read 4499993485312 16384
/dev/sde read 4499993485312 16384
/dev/sde read 4499993485312 16384
/dev/sde read 4499993485312 16384
/dev/sde read 4499993485312 16384
/dev/sde close
with the job file shown below:
[global]
log_offset=1
direct=1
ioengine=sync
[read-phase]
write_lat_log=test
read_iolog=testtrace
Here is what I see in the clat file:
22, 22165, 0, 16384, 1499999997952
48, 25752, 0, 16384, 4499992682496
58, 10044, 0, 16384, 4499992682496
2907, 8123, 0, 16384, 4499992682496
2917, 10077, 0, 16384, 4499992682496
2927, 10002, 0, 16384, 4499992682496
4918, 18610, 0, 16384, 1499999997952
4942, 24021, 0, 16384, 4499993485312
4952, 10018, 0, 16384, 4499993485312
4962, 10017, 0, 16384, 4499993485312
4972, 10030, 0, 16384, 4499993485312
4982, 10029, 0, 16384, 4499993485312
As you can see submission times are like
(22,....,2907,.....,4918,...). So the given value as offset is being
interpreted as absolute delay. In other words it is the time stamp for
the IO right after that. If it is less than the current time of the
job it will be ignored. Otherwise, it will be applied.
Yeah, I was too quick, looking at the code, on reading the log, we store
offset in delay directly:
if (rw == DDIR_WAIT) {
ipo->delay = offset;
} else {
and on retrieval, we factor in the 'td' time offset as an absolute delay.
--
Jens Axboe
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