Generally agreed, but I wanted to understand one point a bit better. On Wed, 22 Jul 2026 at 18:29, Andres Freund <[email protected]> wrote: > - I don't think the hit ratio is an all that interesting way to evaluate the > cache replacement, particularly for something like pgbench -S. It really > matters *which* buffers are evicted.
Is that only because a single bad eviction could cause multiple backends to wait for an I/O? To me, a high probability of multiple accesses within one disk latency would imply that the buffer is really hot and the eviction algorithm would have to be really terrible to evict it. In other words, I have a hard time imagining when it would matter in practice. Of course with prefetching, distinguisghing prefetched misses from synchronous misses is very much important. Ants
