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

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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;
};

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?

--
Jens Axboe

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