Re: patch: improve SLRU replacement algorithm

Greg Stark <stark@mit.edu> writes:
> On Wed, Apr 4, 2012 at 9:34 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
>> Why is this pgbench run accessing so much unhinted data that is > 1
>> million transactions old? Do you believe those numbers? Looks weird.

> I think this is in the nature of the workload pgbench does. Because
> the updates are uniformly distributed, not concentrated 90% in 10% of
> the buffers like most real-world systems, (and I believe pgbench only
> does index lookups) the second time a tuple is looked at is going to
> average N/2 transactions later where N is the number of tuples.

That's a good point, and it makes me wonder whether pgbench is the right
test case to be micro-optimizing around.  It would be a good idea to at
least compare the numbers for something with more locality of reference.
        regards, tom lane