Messages in this thread | | | Date | Wed, 24 Nov 2021 22:19:27 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v0.9.1 3/6] sched/umcg: implement UMCG syscalls |
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On Mon, Nov 22, 2021 at 01:13:24PM -0800, Peter Oskolkov wrote:
> + * Timestamp: a 46-bit CLOCK_MONOTONIC timestamp, at 16ns resolution.
> +static int umcg_update_state(u64 __user *state_ts, u64 *expected, u64 desired, > + bool may_fault) > +{ > + u64 curr_ts = (*expected) >> (64 - UMCG_STATE_TIMESTAMP_BITS); > + u64 next_ts = ktime_get_ns() >> UMCG_STATE_TIMESTAMP_GRANULARITY;
I'm still very hesitant to use ktime (fear the HPET); but I suppose it makes sense to use a time base that's accessible to userspace. Was MONOTONIC_RAW considered?
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