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SubjectRE: [PATCH RFC] smt nice introduces significant lock contention
Date
Nick Piggin wrote on Friday, June 02, 2006 12:53 AM
> Con Kolivas wrote:
>
> >>Nice to acknowledge Chris's idea for
> >>trylocks in your changelog when you submit a final patch.
> >
> >
> > I absolutely would and I would ask for him to sign off on it as well, once we
> > agreed on a final form.
>
> This is a small micro-optimisation / cleanup we can do after
> smtnice gets converted to use trylocks. Might result in a little
> less cacheline footprint in some cases.


Just to pile up more micro-optimization: kernel can break out of the
for_each_domain loop when it hits first SD_SHARE_CPUPOWER.

- Ken


Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>


--- ./kernel/sched.c.orig 2006-06-01 23:14:47.000000000 -0700
+++ ./kernel/sched.c 2006-06-01 23:18:07.000000000 -0700
@@ -2780,8 +2780,10 @@ static int dependent_sleeper(int this_cp
int ret = 0, i;

for_each_domain(this_cpu, tmp)
- if (tmp->flags & SD_SHARE_CPUPOWER)
+ if (tmp->flags & SD_SHARE_CPUPOWER) {
sd = tmp;
+ break;
+ }

if (!sd)
return 0;
-
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