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SubjectRe: [PATCH v5] sched: Avoid unnecessary work in reweight_entity
* Michael Wang <wangyun@linux.vnet.ibm.com> [2012-02-25 21:56:18]:

> Hi, Peter
>
> I have collected more testing data, here is the test results:
>
> Machine: ThinkPad T420
> OS: Ubuntu 11.10
> Benchmark: time make -j14 (build kernel)

Is that benchmark run in root (cpu) cgroup? If so, reweight_entity() should not
kick in at all.

static void update_cfs_shares(struct cfs_rq *cfs_rq)
{

..

if (!se || throttled_hierarchy(cfs_rq))
return;

..

reweight_entity();
}

If you want to stress reweight_entity() create several (cpu) cgroups
and launch workload like kernbench in each of them ..

- vatsa



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