Re: Memory prefetching while sequentially fetching from SortTuple array, tuplestore

On Wed, Sep 2, 2015 at 9:43 PM, David Rowley
<david.rowley@2ndquadrant.com> wrote:
> Peter, would you be able to share the test case which you saw the speedup
> on. So far I've been unable to see much of an improvement.

The case I tested was an internal sort CREATE INDEX. I don't recall
the exact details, but testing showed it to be a fairly robust
speedup. It was not a very brief CREATE INDEX operation, or a very
lengthily one. trace_sort output made it quite visible that there was
a significant saving after the sort is "performed", but before it is
"done". It wasn't hard to see an improvement on a variety of other
cases, although the Intel vTune tool made the difference particularly
obvious.

The only thing that definitely won't be helped is pass-by-value datum
sort cases. In case it matters, I used GCC 4.8.

-- 
Peter Geoghegan