On 07.01.2012 19:18, Tom Lane wrote:
Heikki Linnakangas<heikki.linnakan...@enterprisedb.com> writes:
A couple of weeks ago I wrote a little patch that's similar to
LWLOCK_STATS, but it prints out % of wallclock time that is spent
acquiring, releasing, or waiting for a lock. I find that more useful
than the counters.
I would think that the measurement overhead required to obtain two
wall-clock values for every LWLock touch would be so high as to render
any results from this quite suspect.
It's based on sampling. The timer calls a callback every X ms, which
checks if it's waiting for any lock at that moment, and bumps a counter
if so. In LWLockAcquire/Release you just set/reset a global status variable.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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