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Re: scalablility problem

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>
Cc: Xiaoning Ding <dingxn(at)cse(dot)ohio-state(dot)edu>, Scott Marlowe <smarlowe(at)g2switchworks(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: scalablility problem
Date: 2007-03-31 16:31:48
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
"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

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