Re: HOT pgbench results

Thanks for the testing,

ITAGAKI Takahiro wrote:
> I gathered oprofile logs. There were 4 HOT-related functions, that didn't
> appear in the unpatched test. But it is probably not so serious.
> - heap_page_prune 1.84%
> - PageRepairFragmentation 0.94%
> - pg_qsort 0.44% (called from PageRepairFragmentation)

That's expected. Those functions are involved in removing the dead HOT
tuples, replacing VACUUMs. Maybe we could make them cheaper, but it's
not too bad as it is.

> On the other hand, the number of _bt_compare and _bt_checkkeys were
> reduced by HOT, because we avoid the most part of index insertions.
> It looks like LWLockAcquire/Release were also reduced, but I cannot
> assure it is a benefits of HOT or a measurement deviation.

It could very well be real. Because of the reduction of index
insertions, there's less locking of the index pages.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com