Re: [PATCH 8/5] llist: Remove cpu_relax() usage in cmpxchg loops

Avi Kivity
2011-09-12T14:26:41Z

On 09/12/2011 05:05 PM, Peter Zijlstra wrote:
> Subject: llist: Remove cpu_relax() usage in cmpxchg loops
> From: Peter Zijlstra<a.p.zijlstra@chello.nl>
> Date: Mon Sep 12 15:50:49 CEST 2011
>
> Initial benchmarks show they're a net loss (2 socket wsm):
>
> $ for i in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor ; do echo performance> $i; done
> $ echo 4096 32000 64 128> /proc/sys/kernel/sem
> $ ./sembench -t 2048 -w 1900 -o 0
>

We hyperthreading enabled, and were all threads loaded? cpu_relax
allows the other thread to make more progress while the spinner relaxes.

--
error compiling committee.c: too many arguments to function