On Apr 17, 2014, at 3:06 AM, Sagi Grimberg <sagig@xxxxxxxxxxxxxxxxxx> wrote: > 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. My array size is currently 4. It’s a macro that can be changed easily. By a very large majority, my workloads see only one WC per completion upcall. However, I’m using an older card with simple synthetic benchmarks. I don’t want to make the array large because struct ib_wc is at least 64 bytes on my systems — each WC array would be enormous and hardly ever used. But we can dial it in over time. -- Chuck Lever chuck[dot]lever[at]oracle[dot]com -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
