Re: Bug: Buffer cache is not scan resistant

"Luke Lonergan" <llonergan(at)greenplum(dot)com> writes:
> The issue is summarized like this: the buffer cache in PGSQL is not "scan
> resistant" as advertised.

Sure it is. As near as I can tell, your real complaint is that the
bufmgr doesn't attempt to limit its usage footprint to fit in L2 cache;
which is hardly surprising considering it doesn't know the size of L2
cache. That's not a consideration that we've ever taken into account.

I'm also less than convinced that it'd be helpful for a big seqscan:
won't reading a new disk page into memory via DMA cause that memory to
get flushed from the processor cache anyway? I wonder whether your
numbers are explained by some other consideration than you think.

regards, tom lane