Re: big picture UDP/IP performance question re 2.6.18 -> 2.6.32

From: starlight
Date: Tue Oct 04 2011 - 15:46:41 EST

At 12:38 PM 10/4/2011 -0700, Joe Perches wrote:
>On Tue, 2011-10-04 at 14:16 -0500, Christoph Lameter wrote:
>> On Mon, 3 Oct 2011, starlight@xxxxxxxxxxx wrote:
>> > I've come to the conclusion that Eric is right
>> > and the primary issue is an increase in the
>> > cost of scheduler context switches. Have
>> > been watching this number and it has held
>> > pretty close to 200k/sec under all scenarios
>> > and kernel versions, so it has to be
>> > a longer code-path, bigger cache pressure
>> > or both in the scheduler. Sadly this makes
>> > newer kernels a no-go for us.
>> We had similar experiences. Basically latency
>> constantly gets screwed up by the new fancy
>> features being added to the scheduler and network
>> subsystem (most notorious is the new "fair"
>> scheduler, 2.6.23 made a big
>> step down).
>Idly curious, have you compared bfs performance?

No but it certainly does look very interesting.

Looks like trying it out not much more work than
patching and building a kernel and running the
benchmark. Will take a look and report back
if I do. Little busy at present but should
have time in a week or so.

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