Re: Reduced latency is killing performance

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On 11/10/2016 08:04 AM, Hannes Reinecke wrote:
this really feels like a follow-up to the discussion we've had in Santa
Fe, but finally I'm able to substantiate it with some numbers.

Hello Hannes,

Since for the sequential read test the difference between the 50th percentile sequential read completion time (2.7 ms) and the average completion time (52 ms) is large I assume that you ran the ssd-test.fio job on top of a hard disk or hard disk array? How many hardware queues were active during your test? If multiple hardware queues were active, can you repeat your test with a single hardware queue? The plan for adding I/O scheduling support to blk-mq is - at least initially - only to perform I/O scheduling if there is only a single hardware queue.

Bart.
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