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SubjectRe: [patch v4 09/18] sched: add sched_policies in kernel
On 02/12/2013 06:36 PM, Peter Zijlstra wrote:
> On Thu, 2013-01-24 at 11:06 +0800, Alex Shi wrote:
>> Current scheduler behavior is just consider the for larger performance
>> of system. So it try to spread tasks on more cpu sockets and cpu cores
>> To adding the consideration of power awareness, the patchset adds
>> 2 kinds of scheduler policy: powersaving and balance. They will use
>> runnable load util in scheduler balancing. The current scheduling is taken
>> as performance policy.
>> performance: the current scheduling behaviour, try to spread tasks
>> on more CPU sockets or cores. performance oriented.
>> powersaving: will pack tasks into few sched group until all LCPU in the
>> group is full, power oriented.
>> balance : will pack tasks into few sched group until group_capacity
>> numbers CPU is full, balance between performance and
>> powersaving.
> _WHY_ do you start out with so much choice?
> If your power policy is so abysmally poor on performance that you
> already know you need a 3rd policy to keep people happy, maybe you're
> doing something wrong?

Nope, no much performance yield for both of powersaving and balance policy.
Much of testing results in replaying Ingo's email on '0/18' thread --
the cover letter email threads.

I introduce a 'balance' policy just because HT thread LCPU in Intel CPU
is less then 1 usual cpu power. It is used when someone want to save
power but still want tasks have a whole cpu core...
>> +#define SCHED_POLICY_BALANCE (0x4)
>> +
>> +extern int __read_mostly sched_policy;
> I'd much prefer: sched_balance_policy. Scheduler policy is a concept
> already well defined by posix and we don't need it to mean two
> completely different things.

Got it.

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