Re: A quick fio test (was Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3)

Avi Kivity
2007-02-27T13:56:51Z

Suparna Bhattacharya wrote:
> I tried the latest fio code with syslet v4, and my results are a little
> different - have yet to figure out why or what to make of it.
> I hope I have all the right pieces now.
>
> This is an ext2 filesystem, SCSI AIC7xxx.
>
> I used an iodepth_batch size of 8 to limit the number of ios in a single
> io_submit (thanks for adding that parameter to fio !), like we did in
> aio-stress.
>
> Engine Depth Batch Bw (KiB/sec)
> ----------------------------------------------------
> libaio 64 8 17,226
> syslet 64 8 17,620
> libaio 20000 8 18,552
> syslet 20000 8 14,935
>
>
> Which is not bad, actually.
>
> If I do not specify the iodepth_batch (i.e. default to depth), then the
> difference becomes more pronounced at higher depths. However, I doubt
> whether anyone would be using such high batch sizes in practice ...
>
> Engine Depth Batch Bw (KiB/sec)
> ----------------------------------------------------
> libaio 64 default 17,429
> syslet 64 default 16,155
> libaio 20000 default 15,494
> syslet 20000 default 7,971
>

But what about cpu usage? At these low levels, the cpu is probably
underutilized. It would be interesting to measure cpu time per I/O
request (or, alternatively, use an I/O subsystem that can saturate the
processors).

--
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