> -----Original Message----- > From: linux-rdma-ow...@vger.kernel.org > [mailto:linux-rdma-ow...@vger.kernel.org] On > Behalf Of Chuck Lever > Sent: Thursday, April 17, 2014 8:55 AM > To: Sagi Grimberg > Cc: Steve Wise; Linux NFS Mailing List; linux-rdma@vger.kernel.org > Subject: Re: [PATCH 7/8] xprtrdma: Split the completion queue > > > On Apr 17, 2014, at 3:06 AM, Sagi Grimberg <sa...@dev.mellanox.co.il> 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.
You could use a small array combined with a loop and a budget count. So the code would grab, say, 4 at a time, and keep looping polling up to 4 until the CQ is empty or the desired budget is reached... Stevo -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
