Re: PG 8.1.1 Cannot allocate shared_buffers memory error

Not sure if the kernel shared memory segment size is appropriate, you are allocating all your memory to the chunk.
 
With 32GB memory, effective_cache_size can be raised, higher, and you can go down on shared_buffers. Check this:
http://www.varlena.com/varlena/GeneralBits/Tidbits/annotated_conf_e.html
 
-anjan

    -----Original Message----- 
    From: Tomeh, Husam [mailto:htomeh@firstam.com] 
    Sent: Wed 12/14/2005 5:08 PM 
    To: pgsql-admin@postgresql.org 
    Cc: Tom Lane 
    Subject: [ADMIN] PG 8.1.1 Cannot allocate shared_buffers memory error
    
    

    
    I just installed postgres 8.1.1 on a dual optron Linux box running Linux 
    4 advanced server, with 32GB of RAM and 2GB of swap. 
    I'm trying to allocate 24 GB as shared_bufferes. I'm getting an error 
    that I can not allocate memory (see below). If I change my 
    shared_buffers to 16GB, postgres starts up with no issue. I'm trying to 
    understand why I'm getting the shared memory error at sizes above 16GB 
    whilst I have 32GB with appropriate (I think) settings of kernel 
    parameters. Any help is appreciated. Thanks... 

    My sysctl.conf has : 
      kernel.shmmax = 34359738368 
      kernel.shmall = 34359738368   (32GB). 

    And here's some of related postgresql.conf parameters: 

      shared_buffers = 2359296 
      work_mem = 16384 
      maintenance_work_mem = 2097152 
      max_connections = 100 
      effective_cache_size = 2621440 

    --- 
    Error: 

     FATAL:  could not create shared memory segment: Cannot allocate memory 
    [2005-12-14 13:56:03 PST|||] DETAIL:  Failed system call was 
    shmget(key=5432001, size=19760111616, 03600). 
    [2005-12-14 13:56:03 PST|||] HINT:  This error usually means that 
    PostgreSQL's request for a shared memory segment exceeded available 
    memory or swap space. To reduce the request size (currently 19760111616 
    bytes), reduce PostgreSQL's shared_buffers parameter (currently 2359296) 
    and/or its max_connections parameter (currently 100). 

    --- 
      
    Regards, 

      Husam Tomeh 
       
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    Thank you. 


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