Re: [patch 07/15] sched: expire invalid runtime
From: Peter Zijlstra
Date: Mon May 16 2011 - 07:08:04 EST
On Tue, 2011-05-03 at 02:28 -0700, Paul Turner wrote:
> With the global quota pool, one challenge is determining when the runtime we
> have received from it is still valid. Fortunately we can take advantage of
> sched_clock synchronization around the jiffy to do this cheaply.
> The one catch is that we don't know whether our local clock is behind or ahead
> of the cpu setting the expiration time (relative to its own clock).
> Fortunately we can detect which of these is the case by determining whether the
> global deadline has advanced. If it has not, then we assume we are behind, and
> advance our local expiration; otherwise, we know the deadline has truly passed
> and we expire our local runtime.
This needs a few words explaining why we need to do all this. It only e
explains the how of it.
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