Re: A qsort template

Hi,

On 2021-02-18 16:09:49 +1300, Thomas Munro wrote:
> In another thread[1], I proposed $SUBJECT, but then we found a better
> solution to that thread's specific problem. The general idea is still
> good though: it's possible to (1) replace several existing copies of
> our qsort algorithm with one, and (2) make new specialised versions a
> bit more easily than the existing Perl generator allows. So, I'm back
> with a rebased stack of patches. I'll leave specific cases for new
> worthwhile specialisations for separate proposals; I've heard about
> several.

One place that could benefit is the qsort that BufferSync() does at the
start. I tried your patch for that, and it does reduce the sort time
considerably. For 64GB of mostly dirty shared_buffers from ~1.4s to
0.6s.

Now, obviously one can argue that that's not going to be the crucial
spot, and wouldn't be entirely wrong. OTOH, in my AIO branch I see
checkpointer doing ~10GB/s, leading to the sort being a measurable
portion of the overall time.

Greetings,

Andres Freund