Re: Cannot allocate memory

"JOIGNY Michael @Neteven" <mjoigny@xxxxxxxxxxx> · Tue, 22 Sep 2020 10:20:58 +0200



    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 : 

    
    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.