[Xen-devel] [PATCH] roughly synchronize calibration calls to reduce skew

["Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx>]

This patch (based from 18139) roughly synchronizes calls
to local_time_calibration() across multiple processors
by setting each next timer to a "round epoch".  This results
in reduced skew; both max and average skew are reduced by
between a factor of 2 and 3.  Note that timers still
fire at slightly different times because the next
"round epoch" is still relative to local stime which
still has some inter-processor skew.

Making local_time_calibration() precisely concurrent
across processors is a possible next step but since
each processor still has to get the platform timer -- an
operation that is locked and takes several (and sometimes
tens of) microseconds, concurrency will take some more
cleverness.

Signed-off-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>

===================================
Thanks... for the memory
I really could use more / My throughput's on the floor
The balloon is flat / My swap disk's fat / I've OOM's in store
Overcommitted so much
(with apologies to the late great Bob Hope)

Attachment: roundepoch.patch
Description: Binary data

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