[Xen-devel] [PATCH] add more useful clock output for "xm debug-key t"

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

This patch collects additional useful clock skew output
which is printk'd, for example, by "xm debug-key t".

Since this information assists in the decision whether to
select the new clocksource=tsc and softtsc boot options,
it would be nice to have this in 3.3.

By repeating "xm debug-key t; xm dmesg | tail -N" in
dom0 (e.g. with the "watch" command), useful skew info
about the machine can be collected, which will be very
helpful for diagnosing customer problems on misbehaving
machines.

Patch details:
1) Min and max readings from the current sample are useless
so get rid of those but retain the current maxdif (stime skew).
2) Remember max of skew, sum of skews, and a count
so average skew can be displayed.
3) Also record info for cycles (tsc on x86, itc on ia64).
4) Add a hook for arch-dependent info.  Only used for
clocksource on x86 now, but other info will be added later.

(Note, not compiled on ia64... its possible a header file
will need to be include'd somewhere.)

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

Attachment: debugkeyt.patch
Description: Binary data

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