Re: [GIT PULL] cputime: Convert core use of cputime_t to nsecs

From: Stanislaw Gruszka
Date: Mon Jan 30 2017 - 09:35:05 EST

On Mon, Jan 30, 2017 at 05:46:43AM +0100, Frederic Weisbecker wrote:
> Now lets admit one drawback: s390 and powerpc with
> CONFIG_VIRT_CPU_ACCOUNTING_NATIVE have new cputime_t to nsecs conversion
> on cputime accounting path. But this should be leveraged by the recent
> changes which delay the cputime accounting to tick and context switch.

I think it would be worth to mention that there are other drawbacks on
32bit architectures that use cputime-jiffies currently, like:
- cache utilization will be worse
- conversion cputime_to_jiffies() and cputime_to_clock_t() (with HZ == USER_HS)
will no longer be an no-op
- to keep values consistent will need to add protection of u64 store/load,
which will create additional performance costs