Обсуждение: Xlogprefetcher: Use atomic add for increment counter

Hi,

On 2025-11-07 11:28:06 -0300, Ranier Vilela wrote:
> Use pg_atomic_fetch_add_u64 to replace pg_atomic_read_u64 and
> pg_atomic_write_u64 calls.
> 
> This simplifies the logic and this increases the likelihood that the
> operation will be successful.

How does it do so? As the assertions indicate, this can only be run from a
single process.

Greetings,

Andres Freund

On 2025-11-07 11:52:37 -0300, Ranier Vilela wrote:
> Em sex., 7 de nov. de 2025 às 11:41, Andres Freund <andres@anarazel.de>
> escreveu:
> > On 2025-11-07 11:28:06 -0300, Ranier Vilela wrote:
> > > Use pg_atomic_fetch_add_u64 to replace pg_atomic_read_u64 and
> > > pg_atomic_write_u64 calls.
> > >
> > > This simplifies the logic and this increases the likelihood that the
> > > operation will be successful.
> >
> > How does it do so? As the assertions indicate, this can only be run from a
> > single process.
> >
> Can I rephrase that?
>
> That simplifies the logic a bit.

Maybe simpler, but also vastly slower than before. An atomic increment is
maybe two orders of magnitude more expensive than an unlocked read & write.