Re: UDP-U stream performance regression on 32-rc1 kernel

Ingo Molnar
2009-11-03T17:45:36Z

* Zhang, Yanmin <yanmin_zhang@linux.intel.com> wrote:

> On Tue, 2009-11-03 at 11:47 +0800, Alex Shi wrote:
> > We found the UDP-U 1k/4k stream of netperf benchmark have some
> > performance regression from 10% to 20% on our Tulsa and some NHM
> > machines.
> ﻿ perf events shows function find_busiest_group consumes about 4.5% cpu
> time with the patch while it only consumes 0.5% cpu time without the
> patch.
>
> The communication between netperf client and netserver is very fast.
> When netserver receives a message and there is no new message
> available, it goes to sleep and scheduler calls idle_balance =>
> load_balance_newidle. load_balance_newidle spends too much time and a
> new message arrives quickly before load_balance_newidle ends.
>
> As the comments in the patch say hackbench benefits from it, I tested
> hackbench on Nehalem and core2 machines. hackbench does benefit from
> it, about 6% on nehalem machines, but doesn't benefit on core2
> machines.

Can you confirm that -tip:

http://people.redhat.com/mingo/tip.git/README

has it fixed (or at least improved)?

Ingo