From: | David G Johnston <david(dot)g(dot)johnston(at)gmail(dot)com> |
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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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Thread: | |
Lists: | pgsql-hackers |
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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