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

From: Joe Perches
Date: Tue Oct 04 2011 - 15:38:40 EST

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?

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