On Wed, Nov 26, 2008 at 12:04 PM,  [off-list ref] wrote:

This patch tracks various statistics related to the performance of a RAID 5
or 6 array.  These have been useful to us in the past to help solve
performance issues.  They are reported via /proc/mdstat.

I realize that the format of the statistics may not be the best, and
there may be a better location than /proc/mdstat, so I welcome suggestions
on where to put them.

I will add documentation once we've decided on the format and location (or
if nobody objects to the current format and location.)

Hi Jody,

I have done some work in this area too and have a lingering desire to
hook MD up to the tracing infrastructure du jour.  Have you considered
using tracepoints [1]? This would save the overhead of atomic
operations when we're not profiling.

Regards,
Dan

[1]: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/tracepoints.txt;h=5d354e16749447c667934ecd4c8f4fe5ee3da36c;hb=HEAD