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SubjectRe: [RFC PATCH v1 0/3] Scaled statistics using APERF/MPERF in x86
Pavel Machek wrote:
> Hi!
>>> entitlement for the process as per the current CPU frequency. This
>>> technique is used in powerpc architecture with the help of hardware
>>> registers that accurately capture the entitlement.
>> there are some issues with this unfortunately, and these make it
>> a very complex thing to do.
>> Just to mention a few:
>> 1) What if the BIOS no longer allows us to go to the max frequency for
>> a period (for example as a result of overheating); with the approach
>> above, the admin would THINK he can go faster, but he cannot in reality,
>> so there's misleading information (the system looks half busy, while in
> Plus time one-second-computation-job returning anything else is just
> wrong. Even when it only happens when overheated... or only on battery
> power.
> If you want scaled utime, you need new interface.

We do have a new interface, two new parameters per-task utimescaled and
stimescaled. They already exist in task_struct. Ditto for the delay accounting
pieces. Did I misunderstand your need for a new interface? We still keep utime
and stime around.

Warm Regards,
Balbir Singh
Linux Technology Center

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