Re: How to monitor Postgres real memory usage

Hi Justin

Thanks for your update.

Postgres is just an OS Process, so should be monitored like any other.

What OS are you using ?

> I am using Centos 7.5.

Know that the OS may attribute "shared buffers" to different processes, or
multiple processes.

It's almost always a bad idea to kill postgres with kill -9.

> I unable to connect to database server. I have to kill some process to
release memory. Then I could connect it.

What settings have you used in postgres ?
https://wiki.postgresql.org/wiki/Server_Configuration

> Please reference my attachment.

You can check memory use of an individual query with "explain
(analyze,buffers) .."
https://wiki.postgresql.org/wiki/Slow_Query_Questions

Thanks for your update. This memory allocation failed issue impact the
whole database running. not a slow query.
Is there any commands or method could get totally Postgres memory
utilization ? Thanks .

Justin Pryzby <pryzby(at)telsasoft(dot)com> 于2022年5月25日周三 01:40写道：

> On Wed, May 25, 2022 at 12:25:28AM +0800, 徐志宇徐 wrote:
> > Hi All
> >
> > I am a Database DBA. I focus on PostgreSQL and DB2.
> > Recently. I experience some memory issue. The postgres unable allocate
> > memory. I don't know how to monitor Postgres memory usage.
>
> Postgres is just an OS Process, so should be monitored like any other.
>
> What OS are you using ?
>
> Know that the OS may attribute "shared buffers" to different processes, or
> multiple processes.
>
> > This server have 16G memory. On that time. The free command display
> only 3
> > G memory used. The share_buffers almost 6G.
> >
> > On that time. The server have 100 active applications.
> > New connection failed. I have to kill some application by os command
> "kill -9"
>
> It's almost always a bad idea to kill postgres with kill -9.
>
> > The checkpoint command execute very slow. almost need 5-10 seconds.
>
> Do you mean an interactive checkpoint command ?
> Or logs from log_checkpoint ?
>
> > Is there any useful command to summary PostgreSQL memory usage ?
>
> You can check memory use of an individual query with "explain
> (analyze,buffers) .."
> https://wiki.postgresql.org/wiki/Slow_Query_Questions
>
> What settings have you used in postgres ?
> https://wiki.postgresql.org/wiki/Server_Configuration
>
> What postgres version ?
> How was it installed ? From souce? From a package ?
>
> --
> Justin
>