Re: [PATCH] Log offsets of I/O operations

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On 2014-06-30 16:19, Jens Axboe wrote:
On 2014-06-30 16:09, Abutalib Aghayev wrote:

On Mon, Jun 30 2014 at 17:50 PM, Jens Axboe <axboe@xxxxxxxxx> wrote:
On 2014-06-29 11:43, Abutalib Aghayev wrote:

This is a quick and dirty patch to log offsets of I/O operations as
well.  It is useful if you would like to make offset vs latency plot
for
random I/O, which may not be interesting to many people, so feel
free to
ignore it.

I can definitely see this being useful. But adding 8 bytes to every log
entry complicates things, as fio is already memory intensive there when
logging longer runs.

I'd suggest having two logging types:

struct io_sample {
            uint64_t time;
            uint64_t val;
            uint32_t ddir;
            uint32_t bs;
            uint64_t offset;

I assume you didn't mean offset being here as well.

Ah no, of course not.

struct io_sample_offset {
            struct io_sample s;
            uint64_t offset;
};

and using the right type for what you are logging. This means you'd need
an option to switch on the offset logging, and that you'd need to store
this in the iolog struct (whether to log offset or not) and use the
appropriate size for allocating and extending the log entries when
needed.

Make sense?

Yes, let me rework the patch.

Thanks! Note that you also need to handle the client/server part.
Half-assed attempt attached, not tested at all. Still needs the client
part update.

I finished off the client bit and committed it, it was just a few lines of change and it was done. Also added documentation, etc. So current -git should be complete.

--
Jens Axboe

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