Re: Readme of Buffer Management seems to have wrong sentence

>>You need to have shared_buffers be much smaller than RAM, and have almost
all the "disk" data resident in RAM but not
>> in shared_buffers.
Sure, this is better way to generate heavy activity buffers

-----Original Message-----
From: Jeff Janes [mailto:jeff(dot)janes(at)gmail(dot)com]
Sent: Wednesday, May 23, 2012 11:39 PM
To: Amit Kapila
Cc: Greg Smith; pgsql-hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] Readme of Buffer Management seems to have wrong
sentence

On Wed, May 23, 2012 at 10:33 AM, Amit Kapila <amit(dot)kapila(at)huawei(dot)com>
wrote:
>>>I don't think there is a clear picture yet of what benchmark to use for
> testing changes here.
> I will first try to generate such a scenario(benchmark). I have still not
> thought completely.
> However the idea in my mind is that scenario where buffer list is heavily
> operated upon.
> Operations where shared buffers are much less compare to the data in disk
> and the operations are distributed such that
> they require to access most of the data in disk randomly.

If most buffer reads actually have to read from disk, then that will
so throttle your throughput that you will not be able to make anything
else be relevant. You need to have shared_buffers be much smaller
than RAM, and have almost all the "disk" data resident in RAM but not
in shared_buffers.

Cheers,

Jeff