Thread

1. Xlogprefetcher: Use atomic add for increment counter

   Ranier Vilela <ranier.vf@gmail.com> — 2025-11-07T14:28:06Z

   Hi.
   
   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.
   
   patch attached.
   
   best regards,
   Ranier Vilela
   

2. Re: Xlogprefetcher: Use atomic add for increment counter

   Andres Freund <andres@anarazel.de> — 2025-11-07T14:41:05Z

   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
   
   
   
   

3. Re: Xlogprefetcher: Use atomic add for increment counter

   Ranier Vilela <ranier.vf@gmail.com> — 2025-11-07T14:52:37Z

   Em sex., 7 de nov. de 2025 às 11:41, Andres Freund <andres@anarazel.de>
   escreveu:
   
   > 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.
   >
   Can I rephrase that?
   
   That simplifies the logic a bit.
   
   best regards,
   Ranier Vilela
   

4. Re: Xlogprefetcher: Use atomic add for increment counter

   Andres Freund <andres@anarazel.de> — 2025-11-07T14:59:04Z

   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.
   
   
   
   

5. Re: Xlogprefetcher: Use atomic add for increment counter

   Ranier Vilela <ranier.vf@gmail.com> — 2025-11-07T15:03:01Z

   Em sex., 7 de nov. de 2025 às 11:59, Andres Freund <andres@anarazel.de>
   escreveu:
   
   > 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.
   >
   Seriously, I didn't know.
   
   It's best to withdraw the patch then.
   Thanks for clarifying this.
   
   best regards,
   Ranier Vilela