Re: shared memory segment size alignment

From: David Mosberger <>
Date: 2004-01-17 06:18:57
>>>>> On Fri, 16 Jan 2004 10:31:11 -0800 (PST), umut aymakoglu <> said:

  umut> Hi - In some kernel versions the SHMLBA is defined as
  umut> 1MB(1024*1024) and in some as 16K. What would be the
  umut> difference between aligning the shared memory segment size on
  umut> 1MB versus 16K before calling shmget()? Would there be any
  umut> performance gain/lose? We are aligning the segment address on
  umut> 1MB.

The ia64 architecture allows CPUs to have a performance penalty when
there is virtual aliasing below a 1MB boundary.  So if you don't align
to 1MB, it _could_ run slower.  No existing processor models do that,
but future models might.

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Received on Fri Jan 16 14:24:19 2004

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