Re: tweaking MemSet() performance

Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > Would you please retest this. I have attached my email showing a
> > simpler test that is less error-prone.
>
> What did you consider less error-prone, exactly?
>
> Neil's original test considered the case where both the value being
> set and the buffer length (second and third args of MemSet) are
> compile-time constants. Your test used a compile-time-constant second
> arg and a variable third arg. It's obvious from looking at the source
> of MemSet that this will make a difference in what an optimizing
> compiler can do.

It was less error-prone because you don't have to recompile for every
constant, though your idea that a non-constant length may effect the
optimizer is possible, though I assumed for >=64, the length would not
be significant to the optimizer.

Should we take it to 1024 as a switchover point? I am low at 512, and
others are higher, so 1024 seems like a good average.

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