Good Point, Thanks Michael. Next time I will check the memory usage of other working processes.
looks like it is hard to troubleshooting the postgresql memory usage problem.
Some memory are shared, some are private, some are physical memory, some are virtual memory.
and the ps command shows the misleading memory usage of postgresql process,
is there any tool show memory usage for each postgresql process more clearly?
thanks,
James
From: MichaelDBA <MichaelDBA@sqlexec.com>
Sent: Monday, April 20, 2020 15:37
To: Scott Ribe <scott_ribe@elevated-dev.com>
Cc: jian xu <jamesxu@outlook.com>; Laurenz Albe <laurenz.albe@cybertec.at>; pgsql-admin@postgresql.org <pgsql-admin@postgresql.org>
Subject: Re: checkpoint process use too much memory
You said: "the work_mem is 128MB, so they could use mostly 25GB memory,"
But work_mem is sometimes very deceiving based on types of queries executed. You may need many work_mem buffers for a single query. So 8 buffers used = 1GB. So it could conceivable surpass 25GB easily. I would do some explaining on your SQL workload.
Regards,
Michael Vitale
Scott Ribe wrote on 4/20/2020 3:23 PM:On Apr 20, 2020, at 1:13 PM, jian xu <jamesxu@outlook.com> wrote:
Do you mean the file cache will be counted in postgres checkpointer memory usage?
No, it won't be counted as PG memory. I just mean that free memory low is not a sign of a problem, when it's file cache.