Re: Fix pg_log_backend_memory_contexts() 's delay

On Fri, Oct 8, 2021 at 8:58 PM Fujii Masao <masao.fujii@oss.nttdata.com> wrote:
> >>> Thanks for the patch. Do we also need to do the change in
> >>> HandleMainLoopInterrupts, HandleCheckpointerInterrupts,
> >>> HandlePgArchInterrupts, HandleWalWriterInterrupts as we don't call
> >>> CHECK_FOR_INTERRUPTS() there?
> >
> >> Yeah, that's still some information that the user asked for.  Looking
> >> at the things that have a PGPROC entry, should we worry about the main
> >> loop of the logical replication launcher?
> >
> > ・Now, the target of “pg_log_backend_memory_contexts()” is “autovacuum launcher” and “logical replication launcher”.
I observed that the delay occurred only in “autovacuum launcher” not in “logical replication launcher”. 
> > ・”autovacuum launcher” used “HandleAutoVacLauncherInterrupts()” ( not including
“ProcessLogMemoryContextInterrupt()”) instead of “ProcessInterrupts() ( including “ProcessLogMemoryContextInterrupt()”
).“ProcessLogMemoryContextInterrupt()” will not be executed until the next “ProcessInterrupts()” is executed. So, I
added“ProcessLogMemoryContextInterrupt()”. 
> > ・”logical replication launcher” uses only “ProcessInterrupts()”. So, We don’t have to fix it.
>
> Yes.

+1 to keep this thread for fixing the pg_log_backend_memory_contexts()
issue for the autovacuum launcher. And the patch
"fix_log_output_delay" looks good to me. I think we can add a CF
entry.

> >> IMHO, we can support all the processes which return a PGPROC entry by
> >> both BackendPidGetProc and AuxiliaryPidGetProc where the
> >> AuxiliaryPidGetProc would cover the following processes. I'm not sure
> >> one is interested in the  memory context info of auxiliary processes.
>
> I like this idea because it seems helpful at least for debug purpose.
>
>
> > ・The purpose of this patch is to solve the delay problem, so I would like another patch to deal with “
BackendPidGetProc”and “AuxiliaryPidGetProc”. 
>
> +1 to improve those things separately.

I started a separate thread [1], and I have a couple of open points
there. Please feel free to provide your thoughts in [1].

[1] https://www.postgresql.org/message-id/flat/CALj2ACU1nBzpacOK2q%3Da65S_4%2BOaz_rLTsU1Ri0gf7YUmnmhfQ%40mail.gmail.com

Regards,
Bharath Rupireddy.