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

On Mon, Apr 21, 2014 at 8:07 PM, David G Johnston
<david.g.johnston@gmail.com> wrote:
> 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.


I believe that for the intended use discussed in this thread, a
compile-time switch would be more than enough control, and it would
avoid that tradeoff.