Re: kernel 3.18 io bottlenecks?

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On Wed, Jun 24, 2015 at 8:38 PM, Stefan Priebe <s.priebe@xxxxxxxxxxxx> wrote:
>
> Am 24.06.2015 um 16:55 schrieb Nick Fisk:
>>
>> That kernel probably has the bug where tcp_nodelay is not enabled. That
>> is fixed in Kernel 4.0+, however also in 4.0 blk-mq was introduced which
>> brings two other limitations:-
>
>
> blk-mq is terrible slow. That's correct.

Is that a general sentiment or your experience with rbd?  If the
latter, can you describe your workload and provide some before and
after blk-mq numbers?  We'd be very interested in identifying and
fixing any performance regressions you might have on blk-mq rbd.

(As I mentioned in another reply, the two limitations Nick brought up
are fixed - the patches are on their way to mainline and are simple
enough for you to apply or I can build a kernel with those patches
applied for you so you can test.)

Thanks,

                Ilya
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