Message-ID: <460E9589.6070103@cse.ohio-state.edu>
Date: Sat, 31 Mar 2007 13:08:25 -0400
From: Xiaoning Ding <dingxn@cse.ohio-state.edu>
User-Agent: Thunderbird 1.5.0.10 (X11/20070301)
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To: Tom Lane <tgl@sss.pgh.pa.us>
CC: "Joshua D. Drake" <jd@commandprompt.com>,
	Scott Marlowe <smarlowe@g2switchworks.com>,
	pgsql-performance@postgresql.org
Subject: Re: scalablility problem
References: <460D7220.9010302@cse.ohio-state.edu>
	<1175290903.25022.110.camel@state.g2switchworks.com>
	<460E8198.1010604@cse.ohio-state.edu>
	<460E82ED.8070106@commandprompt.com>
	<6434.1175358708@sss.pgh.pa.us>
In-Reply-To: <6434.1175358708@sss.pgh.pa.us>
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Tom Lane wrote:
> "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
That is very helpful. Thanks!

Xiaoning
> 
>