Re: New PG14 server won't start with >2GB shared_buffers

Ron <ronljohnsonjr@xxxxxxxxx> · Sat, 25 Feb 2023 04:25:10 -0600



    Why did you have to drop shared buffers to 500MB, instead of
    something just below 2GB?

    
    And what's "your kernel's SHMALL parameter"?

    
    On 2/24/23 20:08, Chris Hoover wrote:

    
      Hello All,
      

      Have a strange issue that I can not solve.
      

      I have a new server that has 1TB ram (not a typo).  I have
        been fighting with this evening to start up with a shared_buffer
        setting over 2GB.  When the memory allocation  breaks 2GB, the
        database won’t start.  I’ve dropped it down to 500M to get the
        database online.  We’ve tried both SysV memory and mmap memory.
      

      Any ideas on what is going on and how to resolve?  I’m sure
        I’m missing something obvious, but it is totally eluding me.
      

      OS: Ubuntu 18.04
      Memory:  1007GB

      
      CPU: Intel(R) Xeon(R) CPU           X7550  @ 2.00GHz (64
        cores total)
      

      Kernel Memory:
      
        kernel.shmmax = 274877906944
        kernel.shmall = 17179869184
      
      
      Postgres Config:
      
                          name                                  |  
                         setting
         autovacuum_max_workers                 | 3
         autovacuum_work_mem                     | -1
         effective_cache_size                           | 98992128
         fsync                                                    |
          on
         full_page_writes                                  | on
         maintenance_work_mem                    | 2097152
         shared_buffers                                    | 64000
         shared_memory_type                         | sysv
         temp_buffers                                       | 4096
         wal_buffers                                         | 2048
         work_mem                                          | 119990
      
      
      If you need additional parameters, please ask
      

      SysV Error:
      
        Feb 25 01:55:16 appdb-server01.production.aweberint.com
          postgres[34680]: FATAL:  could not create shared memory
          segment: Cannot allocate memory
        DETAIL:  Failed system call was shmget(key=2359323,
          size=2063564800, 03600).
        HINT:  This error usually means that PostgreSQL's request
          for a shared memory segment exceeded your kernel's SHMALL
          parameter.  You might need to reconfigure the kernel with
          larger SHMALL.
      
      
      Mmap Error:
      
        FATAL:  could not map anonymous shared memory: Cannot
          allocate memory
        HINT:  This error usually means that PostgreSQL's request
          for a shared memory segment exceeded available memory, swap
          space, or huge pages. To reduce the request size (currently
          1635737600 bytes), reduce PostgreSQL's shared memory usage,
          perhaps by reducing shared_buffers or max_connections.
        

          Thanks,
          

          Chris Hoover
          Senior DBA
          AWeber.com
          Cell: (803) 528-2269
          Email: chrish@xxxxxxxxxx
          

    -- 

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