| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Jim Nasby <jim(at)nasby(dot)net> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Storing hot members of PGPROC out of the band |
| Date: | 2011-12-17 14:00:39 |
| Message-ID: | CA+TgmoZqb=bXhOT+u9WBpc-ncuV2fE6E=ugTe5tGUzPwZhWzyg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sat, Dec 17, 2011 at 1:00 AM, Jim Nasby <jim(at)nasby(dot)net> wrote:
> I also wonder how much this throws some previous performance tests into suspicion. If it's not uncommon for performance improvement attempts to shift a bottleneck to a different part of the system and marginally hurt performance then we might be throwing away good performance improvement ideas before we should...
I think we are (mostly) OK on this point, at least as far as the work
I've been doing. We've actually had a few previous instances of this
phenomenon - e.g. when I first committed my fastlock patch,
performance actually got worse if you had >40 cores doing read-only
queries, because speeding up the lock manager made it possible for the
spinlock protection SInvalReadLock to mess things up royally.
Nevertheless, we got it committed - and fixed the SInvalReadLock
problem, too. This one is/was somewhat more subtle, but I'm feeling
pretty good about our chances of making at least some further progress
in time for 9.2.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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