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

[Abutalib Aghayev <agayev@gmail.com>]

On Mon, Jun 30 2014 at 17:50 PM, Jens Axboe <axboe@kernel.dk> 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.

> };
>
> 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.