Re: [PATCH v0.9.1 3/6] sched/umcg: implement UMCG syscalls
flat view
From: Peter Zijlstra <peterz@infradead.org>
Date: 2021-11-24 21:19:44
Also in:
linux-mm, lkml
On Mon, Nov 22, 2021 at 01:13:24PM -0800, Peter Oskolkov wrote:
+ * Timestamp: a 46-bit CLOCK_MONOTONIC timestamp, at 16ns resolution.
quoted hunk ↗ jump to hunk
+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?