Re: posix_fadvise v22

Greg Smith <gsmith@gregsmith.com> writes:
> On Thu, 1 Jan 2009, Robert Haas wrote:
>> The only thing I haven't been able to do is demonstrate that this change 
>> actually produces a performance improvement.  Either I'm testing the 
>> wrong thing, or it just doesn't provide any benefit on a single-spindle 
>> system.

> When I did a round of testing on the earlier prefetch test program Greg 
> Stark put together, one of my single-spindle Linux system didn't show any 
> real benefit.  So as long as you didn't see performance degrade, your not 
> seeing any improvement isn't bad news.

ISTM that you *should* be able to see an improvement on even
single-spindle systems, due to better overlapping of CPU and I/O effort.
If the test case is either 100% CPU-bound or 100% I/O-bound then no,
but for anything in between there ought to be improvement.
        regards, tom lane