"Joshua D. Drake" <jd@commandprompt.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