Re: MMAP Buffers - Mailing list pgsql-hackers

From Andres Freund
Subject Re: MMAP Buffers
Date
Msg-id 201104172002.11811.andres@anarazel.de
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In response to Re: MMAP Buffers  (Radosław Smogura <rsmogura@softperience.eu>)
Responses Re: MMAP Buffers  (Radosław Smogura <rsmogura@softperience.eu>)
List pgsql-hackers
On Sunday 17 April 2011 19:26:31 Radosław Smogura wrote:
> Kernel merges vm_structs. So mappings are compacted. I'm not kernel
> specialist, but skipping memory consumption, for not compacted mappings,
> kernel uses btrees for dealing with  TLB, so it should not matter if there
> is  100 vm_structs or 100000 vm_structs.
But the CPUs TLB cache has maybe 16/256 (1lvl, 2nd) to 64/512 entries. That
will mean that there will be cachemisses all over.
Additionally your scheme requires flushing it regularly...

Andres


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