On Mon, Sep 27, 2010 at 09:52:21AM +0100, Robert Watson wrote:
> One reason I haven't merged the earlier patch is that many high-performance
> 10gbps (and even 1gbps) cards now support multiple input queues in hardware,
> meaning that they have already done the work distribution by the time the
> packets get to the OS. This makes the work distribution choice quite a bit
> harder: has a packet already been adequately balanced, or is further
> rebalancing required -- and of so, an equal distribution as selected in that
> patch might not generate well-balanced CPU load.
>
> Using just the RSS hash to distribute work, and single-queue input, I am able
> to get doubled end-host TCP performance with highly concurrent connections at
> 10gbps, which is a useful result. I have high on my todo list to get the
> patch you referenced into the mix as well and see how much the software
> distrbiution hurts/helps...
Thanks for explanation.
> Since you've done some measurement, what was the throughput on that system
> without the patch applied, and how many cores?
The server has four cores. Topology:
0, 1, 2, 3
0, 1, 2, 3
Without patch i have only one netisr thread
utilization with 100% cpu load and ~90% packets drop at max 80-90Kpps. The
throughput oscillated from 2MB/s to 30MB/s.
Cores 0,2,3 - netisr with cpu binding
Core 1 - irq256 (bge0) bind via cpuset(1)
P.S.: bge(4) patched for agressive interrupt moderation. Without this i have
11K+ int/sec and ~99% cpu usage only in the interrupt handling.
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