Re: Cannot allocate memory

Hi,

I would like to come back to you about my memory problem on postgres 12.

We had the same configuration under postgres 11.8, we disabled JIT
(enabled by default under postgres 12) for segfault problems.

To illustrate the change in memory behavior, here is a screenshot before
/ after migration :

memory

Do you have any idea what could change the behavior in this way? another
parameter enabled by default under postgres 12 like JIT?

Regards.

Le 18/09/2020 à 12:03, JOIGNY Michael @Neteven a écrit :
>
> Hi Community,
>
> I'm asking for your lights because i'm having memory problems with
> postgres.
>
> Examples of logs :
>
> /FATAL: could not fork new process for connection: Cannot allocate
> memory could not fork new process for connection: Cannot allocate memory
> out of memory  DETAIL:  Failed on request of size 32800 in memory
> context "HashBatchContext".
> out of memory DETAIL Failed on request of size 288 in memory context
> "CacheMemoryContext".
> /
>
> We use postgresql (primary/standby) with pgbouncer as a pooler, and
> repmgr as replication manager.
>
> We have ~ 2000 connections at the same time with ~ 20/30 are active.
> (we need to set a high number of connexion on postgres, because our
> app uses a lot of different users, and each user on each app server
> needs multiple and constant connexions).
>
> Here is my configuration :
>
> _system : _
>
> Debian : 9.13
> Memory : 380 Go
> Postgres : 12.4-1.pgdg90+1
> Pgbouncer : 1.14
> kernel.shmmax = 202591600640
> kernel.shmall = 49460840
>
> _postgres :
> _
>
> dynamic_shared_memory_type = posix    # the default is the first option
> max_connections = 2600            # (change requires restart)
> work_mem = 96MB                # min 64kB
> maintenance_work_mem = 8GB        # min 1MB
> shared_buffers = 64GB            # min 128kB
> temp_buffers = 32MB            # min 800kB
> wal_buffers = 16MB            # min 32kB, -1 sets based on shared_buffers
> effective_cache_size = 270GB
>
> pgbouncer :
>
> max_client_conn = 6000
> default_pool_size = 2590
> reserve_pool_size = 5
> pool_mode = session
>
> Do you think that our parameters are not correct compared to our
> configuration? Do you have an idea ?
>
> Best regards.
>
> Michael.
>