Re: 2.6.19-rc5: known regressions

Eric W. Biederman
2006-11-08T11:18:46Z

Adrian Bunk <bunk@stusta.de> writes:

> Subject : x86_64: NR_IRQ increase causes 11.5% slowdown
> in lmbench's fork benchmark
> References : http://lkml.org/lkml/2006/11/2/192
> Submitter : Tim Chen <tim.c.chen@linux.intel.com>
> Caused-By : Eric W. Biederman <ebiederm@xmission.com>
> commit 550f2299ac8ffaba943cf211380d3a8d3fa75301
> Status : unknown

I'm not really certain who to cc on this one.

It appears the problem sequence is:
fork()
sched_setaffinity()

It got worse just because NR_IRQS doubled (and all of the associated
arrays doubled in size).

I haven't seen anyone reproduce this but Tim Chen, and Tim wasn't
able to root cause the problem so I believe we are going to have
this regression :(

Eric