Re: scalablility problem

[Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>]

"Joshua D. Drake" <jd(at)commandprompt(dot)com> writes:
>> I use RHEL 4. I can not understand how the scalability related with 
>> shared memory?

> It isn't RHEL4 and shared memory. It is PostgreSQL and shared memory. 
> Things have changed with PostgreSQL since 7.3 (7.3 is really god awful 
> old) that allow it to more effectively access shared memory and thus 
> provide better performance.

Some specifics:

* bufmgr algorithms redesigned to allow larger number of shared buffers
to be used effectively

* bufmgr redesigned to not have a single lock for management of all
shared buffers; likewise for lockmgr

* lots of marginal tweaks such as paying attention to cache line
alignment of "hot" shared data structures

I'm probably forgetting some things but I think the bufmgr and lockmgr
changes were the biggest improvements in this area.

			regards, tom lane