On Tue, Feb 19 2013, Alireza Haghdoost wrote:
> Hi,
>
> I am trying to understand how fio respect timing information between
> consecutive IOs in a read_iolog job, However the logic is not very
> clear for me , specially in the following function:
>
> static int read_iolog2(struct thread_data *td, FILE *f)
> {
> ...
> r = sscanf(p, "%256s %256s %llu %u", fname, act, &offset,
> &bytes);
> ...
> if (!strcmp(act, "wait"))
> rw = DDIR_WAIT;
> ...
> if (rw == DDIR_WAIT) {
> ipo->delay = offset;
> ...
> queue_io_piece(td, ipo);
> }
>
> Here is my two questions about this function:
> First, I can not see any "wait" command in a typical iolog file
> (collected with write_iolog=str job option). Should I set special
> parameter in job file to collect iolog with respect to IO timing
> information.
> Second, Why request offset assigned to ipo->delay ? I was thinking
> that ipo->delay should get some timing value which represent
> inter-submission time delay. However, In this case ipo->delay get LBA
> offset which just a byte address in my point view.
That is the format of a delay line, instead of an LBA it has a timing
parameter. Normally you don't have delays at all, it's only for replay
and record of blktraces that would be a factor.
--
Jens Axboe
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