Re: Performance regression from switching lock to rw-sem for anon-vmatree

From: Alex Shi
Date: Mon Jun 17 2013 - 19:20:32 EST

On 06/18/2013 12:22 AM, Davidlohr Bueso wrote:
> After a lot of benchmarking, I finally got the ideal results for aim7,
> so far: this patch + optimistic spinning with preemption disabled. Just
> like optimistic spinning, this patch by itself makes little to no
> difference, yet combined is where we actually outperform 3.10-rc5. In
> addition, I noticed extra throughput when disabling preemption in
> try_optimistic_spin().
> With i_mmap as a rwsem and these changes I could see performance
> benefits for alltests (+14.5%), custom (+17%), disk (+11%), high_systime
> (+5%), shared (+15%) and short (+4%), most of them after around 500
> users, for fewer users, it made little to no difference.

A pretty good number. what's the cpu number in your machine? :)

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