Thread

1. Re: [HACKERS] Neverending query on 6.5.2 over Solaris 2.5.1

   Tom Lane <tgl@sss.pgh.pa.us> — 1999-10-22T15:33:56Z

   Fernando Schapachnik <fpscha@ns1.via-net-works.net.ar> writes:
   >> enough buffer space to avoid thrashing.  You need to increase your
   >> kernel's max-shared-memory-block-size (SHMMAX, I think) parameter
   >> so that you can run with a more reasonable -B setting.  A lot of
   >> kernels ship with SHMMAX settings that are ridiculously small for
   >> any modern machine.
   
   > What value would you advise for shmmax?
   
   Well, with the default number of buffers (64) Postgres requires about
   a megabyte (I think a tad over 1Mb, in 6.5.*).  Extra buffers are 8K
   plus a little overhead apiece.  If you are running with more than a
   couple of active backends at a time then you probably want to use
   more than the default number of buffers.  But I have no advice on
   how many is appropriate for what size of installation --- can anyone
   else help?
   
   			regards, tom lane
   
   

2. Re: [HACKERS] Neverending query on 6.5.2 over Solaris 2.5.1

   Brian E Gallew <geek+@cmu.edu> — 1999-10-22T15:57:11Z

   Then <tgl@sss.pgh.pa.us> spoke up and said:
   > Fernando Schapachnik <fpscha@ns1.via-net-works.net.ar> writes:
   > > What value would you advise for shmmax?
   > 
   > more than the default number of buffers.  But I have no advice on
   > how many is appropriate for what size of installation --- can anyone
   > else help?
   
   Unless you are severely resource constrained, think big.  Generally
   speaking, the kilobytes of memory you'll lose to kernel structures are
   irrelevant.  Performance is generally not an issue, either.
   
   -- 
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