[PATCH] Adaptive spinning for lockmgr

[Attilio Rao]

This patch enables adaptive spinning for lockmgr:
http://www.freebsd.org/~attilio/adaptive_lockmgr.diff

and it should presumably improve performance on disks/vfs/buffer cache
based benchmarks, so, if you want to try out and report any benchmarks
result, I'd love to see it.
Please note that there are some parameters to tune: for example, you
would like to not enable adaptive spinning to default while you just
want that for a class of locks (and in that case you want to apply the
reversed logic for what is living now) or you want to use different
values  for retries and loops. Interested developers can refer to such
3 variables.
Peter Holm alredy tested that patch for about 24hours without any
regression to report.

Also note that the patch is not 100% yet as long as it needs UPDATES
and manpages updates, but they will be added just in time before to
commit.
The modify is all there.

Thanks,
Attilio


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