Re: Proposal of tunable fix for scalability of 8.4

Tom Lane wrote:
> Scott Carey <scott@richrelevance.com> writes:
>
>> If there is enough lock contention and a common lock case is a short lived shared lock, it makes perfect sense
sense. Fewer readers are blocked waiting on writers at any given time.  Readers can 'cut' in line ahead of writers
withina certain scope (only up to the number waiting at the time a shared lock is at the head of the queue).
Essentiallythis clumps up shared and exclusive locks into larger streaks, and allows for higher shared lock throughput. 
>> Exclusive locks may be delayed, but will NOT be starved, since on the next iteration, a streak of exclusive locks
willoccur first in the list and they will all process before any more shared locks can go. 
>>
>
> That's a lot of sunny assertions without any shred of evidence behind
> them...
>
> The current LWLock behavior was arrived at over multiple iterations and
> is not lightly to be toyed with IMHO.  Especially not on the basis of
> one benchmark that does not reflect mainstream environments.
>
> Note that I'm not saying "no".  I'm saying that I want a lot more
> evidence *before* we go to the trouble of making this configurable
> and asking users to test it.
>
>             regards, tom lane
>
>
Fair enough..  Well I am now appealing  to all  who has a fairly decent
sized hardware want to try it out  and see whether there are "gains",
"no-changes" or "regressions" based on your workload. Also it will help
if you report number of cpus when you respond back to help collect
feedback.

Regards,
Jignesh

--
Jignesh Shah           http://blogs.sun.com/jkshah
The New Sun Microsystems,Inc   http://sun.com/postgresql