* Juri Lelli juri.lelli@arm.com [2016-09-16 16:14:34]:
I haven't given much thought on how impossible this would be to achieve on other architectures. Does anyone foresee this to be a show-stopper on any architecture?
I'm mostly afraid of the fact that you basically reintroduce double locking on migration after it has been removed (for CFS) a couple of years ago with commit 163122b7fcfa "sched/fair: Remove double_lock_balance() from load_balance()".
I think it should be possible to adjust counters without relying on double-locking. We will include that change in next version.
Regarding overheads associated with synchronization, there is only a small overhead during bootup when secondary cpus need to sync up on 'window_start' for first time. After that they roll on their own (provided there is some constant offset between hardware clock of various cpus).
Not sure we can assume this for all architectures.
I guess we can rely on ktime as fall-back option on architectures where the constant offset prerequisite can't be met. We can discuss that further on lkml.
- vatsa
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