Re: patch: improve SLRU replacement algorithm

On Wed, Apr 4, 2012 at 6:25 PM, Alvaro Herrera
<alvherre(at)commandprompt(dot)com> wrote:
>
> Excerpts from Greg Stark's message of mié abr 04 14:11:29 -0300 2012:
>> On Wed, Apr 4, 2012 at 1:00 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> > , everybody's next few CLOG requests hit some other
>> > buffer but eventually the long-I/O-in-progress buffer again becomes
>> > least recently used and the next CLOG eviction causes a second backend
>> > to begin waiting for that buffer.
>>
>> This still sounds like evidence that the slru is just too small for
>> this transaction rate.
>
> What this statement means to me is that the number of slru buffers
> should be configurable, not compile-time fixed.

I think the compile time fixed allows it to be loop unrolled and
executed in parallel.

Using a parameter makes the lookups slower. Worth testing. Life changes.

--
 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services