Re: hackbench regression due to commit 9dfc6e68bfe6e

From: Pekka Enberg
Date: Mon Apr 05 2010 - 13:30:16 EST

(I'm CC'ing Tejun)

On Mon, Apr 5, 2010 at 4:54 PM, Christoph Lameter
<cl@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Fri, 2 Apr 2010, Zhang, Yanmin wrote:
>> My testing command on my 2 socket machine:
>> #hackbench 100 process 20000
>> With 2.6.33, it takes for about 96 seconds while 2.6.34-rc2 (or the latest tip tree)
>> takes for about 101 seconds.
>> perf shows some functions around SLUB have more cpu utilization, while some other
>> SLUB functions have less cpu utilization.
> Hmnmmm... The dynamic percpu areas use page tables and that data is used
> in the fast path. Maybe the high thread count causes tlb trashing?

Hmm indeed. I don't see anything particularly funny in the SLUB percpu
conversion so maybe this is a more issue with the new percpu
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