* A probable minor mistake in HOWTO page @ 2015-04-07 17:23 Mansour Shafaei Moghaddam 2015-04-24 16:46 ` Jens Axboe 0 siblings, 1 reply; 5+ messages in thread From: Mansour Shafaei Moghaddam @ 2015-04-07 17:23 UTC (permalink / raw) To: fio Hi, I found a minor mistake in the Fio's HOWTO page. According to this document the "wait" command considers the offset as the number of milliseconds which it must hold on before submitting the next I/O. A very simple experiment with a short trace including those "wait" commands shows that the numbers that you put as offset are interpreted as the time for submission of next I/O not the amount of wait time between them. In other words, the value in offset field is the absolute delay from the beginning of run not the relative delay. P.S.: The version of fio I have been working on is 2.1.11, but I saw the same explanation in more recent versions' HOWTO page as well. So, decided to share it with you. Mansour ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: A probable minor mistake in HOWTO page 2015-04-07 17:23 A probable minor mistake in HOWTO page Mansour Shafaei Moghaddam @ 2015-04-24 16:46 ` Jens Axboe 2015-04-24 17:10 ` Mansour Shafaei Moghaddam 0 siblings, 1 reply; 5+ messages in thread From: Jens Axboe @ 2015-04-24 16:46 UTC (permalink / raw) To: Mansour Shafaei Moghaddam, fio On 04/07/2015 11:23 AM, Mansour Shafaei Moghaddam wrote: > Hi, > > I found a minor mistake in the Fio's HOWTO page. According to this > document the "wait" command considers the offset as the number of > milliseconds which it must hold on before submitting the next I/O. A > very simple experiment with a short trace including those "wait" > commands shows that the numbers that you put as offset are interpreted > as the time for submission of next I/O not the amount of wait time > between them. In other words, the value in offset field is the > absolute delay from the beginning of run not the relative delay. > > P.S.: The version of fio I have been working on is 2.1.11, but I saw > the same explanation in more recent versions' HOWTO page as well. So, > decided to share it with you. Thanks, updated. It is indeed a relative time. -- Jens Axboe ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: A probable minor mistake in HOWTO page 2015-04-24 16:46 ` Jens Axboe @ 2015-04-24 17:10 ` Mansour Shafaei Moghaddam 2015-04-24 17:16 ` Jens Axboe 0 siblings, 1 reply; 5+ messages in thread From: Mansour Shafaei Moghaddam @ 2015-04-24 17:10 UTC (permalink / raw) To: Jens Axboe; +Cc: fio 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. On Fri, Apr 24, 2015 at 12:46 PM, Jens Axboe <axboe@kernel.dk> wrote: > On 04/07/2015 11:23 AM, Mansour Shafaei Moghaddam wrote: >> >> Hi, >> >> I found a minor mistake in the Fio's HOWTO page. According to this >> document the "wait" command considers the offset as the number of >> milliseconds which it must hold on before submitting the next I/O. A >> very simple experiment with a short trace including those "wait" >> commands shows that the numbers that you put as offset are interpreted >> as the time for submission of next I/O not the amount of wait time >> between them. In other words, the value in offset field is the >> absolute delay from the beginning of run not the relative delay. >> >> P.S.: The version of fio I have been working on is 2.1.11, but I saw >> the same explanation in more recent versions' HOWTO page as well. So, >> decided to share it with you. > > > Thanks, updated. It is indeed a relative time. > > -- > Jens Axboe > ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: A probable minor mistake in HOWTO page 2015-04-24 17:10 ` Mansour Shafaei Moghaddam @ 2015-04-24 17:16 ` Jens Axboe 2015-04-24 17:18 ` Mansour Shafaei Moghaddam 0 siblings, 1 reply; 5+ messages in thread From: Jens Axboe @ 2015-04-24 17:16 UTC (permalink / raw) To: Mansour Shafaei Moghaddam; +Cc: fio 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 ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: A probable minor mistake in HOWTO page 2015-04-24 17:16 ` Jens Axboe @ 2015-04-24 17:18 ` Mansour Shafaei Moghaddam 0 siblings, 0 replies; 5+ messages in thread From: Mansour Shafaei Moghaddam @ 2015-04-24 17:18 UTC (permalink / raw) To: Jens Axboe; +Cc: fio Thanks for your response and also your consideration. Good Luck On Fri, Apr 24, 2015 at 1:16 PM, Jens Axboe <axboe@kernel.dk> wrote: > 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 > ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2015-04-24 17:18 UTC | newest] Thread overview: 5+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2015-04-07 17:23 A probable minor mistake in HOWTO page Mansour Shafaei Moghaddam 2015-04-24 16:46 ` Jens Axboe 2015-04-24 17:10 ` Mansour Shafaei Moghaddam 2015-04-24 17:16 ` Jens Axboe 2015-04-24 17:18 ` Mansour Shafaei Moghaddam
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