Re: Not HOT enough

Robert Haas <robertmhaas@gmail.com> writes:
> On Wed, Nov 23, 2011 at 1:30 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> What I think might make more sense is to keep two variables,
>> RecentGlobalXmin with its current meaning and RecentDatabaseWideXmin
>> which considers only xmins of transactions in the current database.
>> Then HOT cleanup could select the appropriate cutoff depending on
>> whether it's working on a shared or non-shared relation.

> Unfortunately, that would have the effect of lengthening the time for
> which ProcArrayLock is held, and as benchmark results from Pavan's
> patch in that area show, that makes a very big difference to total
> throughput on write-heavy workloads.

[ shrug... ]  Simon's patch already adds nearly as many cycles in the
hot spot as would be required to do what I suggest.

			regards, tom lane