Re: [HACKERS] Clock with Adaptive Replacement

Hi!

> 30 апр. 2018 г., в 23:15, Andres Freund <andres@anarazel.de> написал(а):
> On 2018-04-30 15:39:08 +0500, Andrey Borodin wrote:
>> I suspect that performance benefits can be not that big or even
>> marginal, if we do not extend comprehensive eviction strategy with
>> bgwriter fixes and O_DIRECT.
>
> If so, then the improvements aren't real. Bgwriter doesn't matter for
> read-only workloads. O_DIRECT doesn't matter much if shared_buffers are
> 60+% of OS memory.  And even disregarding that, you can just compute
> cache hit ratios to see whether things are improving.
Even considering simply changing eviction strategy - it is not just about hit ratio. It is also about eviction
complexityless than O(N). 

But I think you are right. If we compare performance effect of half-measures in the real system, probably it is more
accuratethan comparing isolated algorithms in a sand box. 

Best regards, Andrey Borodin.