Re: [PATCH 7/8] xprtrdma: Split the completion queue

Sagi Grimberg
2014-04-17T07:06:07Z

On 4/16/2014 9:21 PM, Chuck Lever wrote:
> Passing a small array to ip_poll_cq() is actually easy to do, and is
> exactly equivalent to a poll budget. The struct ib_wc should be taken
> off the stack anyway, IMO.
>
> The only other example I see in 3.15 right now is IPoIB, which seems
> to do exactly this.
>
> I’m testing a patch now. I’d like to start simple and make it more
> complex only if we need to.

What array size are you using? Note that if you use a small array it may
be an overkill since
a lot more interrupts are invoked (-> more latency). I found that for a
high workload a budget
of 256/512/1024 keeps fairness and doesn't increase latency.

Regardless, doing array-polling is a nice optimization reducing CQ
entrances.

Sagi.
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