Re: Clock sweep not caching enough B-Tree leaf pages?

From: David G Johnston <david(dot)g(dot)johnston(at)gmail(dot)com>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Clock sweep not caching enough B-Tree leaf pages?
Date: 2014-04-21 23:07:16
Message-ID: 1398121636361-5800988.post@n5.nabble.com
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Jim Nasby-2 wrote
>> I feel that if there is no memory pressure, frankly it doesnt matter much
>> about what gets out and what not. The case I am specifically targeting is
>> when the clocksweep gets to move about a lot i.e. high memory pressure
>> workloads. Of course, I may be totally wrong here.
>
> Well, there's either memory pressure or there isn't. If there isn't then
> it's all moot *because we're not evicting anything*.

The trade-off I'm seeing here is between measuring when there is no memory
pressure - and thus eating at performance while not actually evicting
buffers - and not measuring but then encountering memory pressure and not
having a clue as to what should be evicted.

David J.

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