Re: Use fadvise in wal replay

On Fri, Nov 25, 2022 at 1:12 PM Pavel Borisov <pashkin.elfe@gmail.com> wrote:
>
> As I've written up in the thread we can not gain much from this
> optimization. The results of Jakub shows around 2% difference:
>
> >baseline, master, default Linux readahead (128kb):
> >33.979, 0.478
> >35.137, 0.504
> >34.649, 0.518>
>
> >master+patched, readahead disabled:
> >34.338, 0.528
> >34.568, 0.575
> >34.007, 1.136
>
> >master+patched, readahead enabled (as default):
> >33.935, 0.523
> >34.109, 0.501
> >33.408, 0.557
>

The performance benefit shows up only when readahead is disabled. And
on many workloads readahead brings unneeded data into page cache, so
it's preferred configuration.
In this particular case, time to apply WAL decreases from 53s to 33s.

Thanks!

Best Regards, Andrey Borodin.