Re: Bug: Buffer cache is not scan resistant

Grzegorz Jaskiewicz <gj@pointblue.com.pl> writes:
> On Mar 5, 2007, at 2:36 AM, Tom Lane wrote:
>> 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?

> Nope. DMA is writing directly into main memory. If the area was in  
> the L2/L1 cache, it will get invalidated. But if it isn't there, it  
> is okay.

So either way, it isn't in processor cache after the read.  So how can
there be any performance benefit?
        regards, tom lane