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Re: Solaris shared_buffers anomaly?

From: Mischa Sandberg <mischa(at)ca(dot)sophos(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Solaris shared_buffers anomaly?
Date: 2006-06-14 17:06:20
Message-ID: 4490420C.1030609@ca.sophos.com (view raw or flat)
Thread:
Lists: pgsql-performance
Tom Lane wrote:
> Mischa Sandberg <mischa(at)ca(dot)sophos(dot)com> writes:

>> Tom Lane wrote:
>>> Does Solaris have any call that allows locking a shmem segment in RAM?
>> Yes, mlock(). But want to understand what's going on before patching.
> 
> Sure, but testing it with mlock() might help you understand what's going
> on, by eliminating one variable: we don't really know if the shmem is
> getting swapped, or something else.

>> For a dedicated DB server machine, Solaris has a feature:
>> create "intimate" shared memory with shmat(..., SHM_SHARE_MMU).
>> All backends share the same TLB entries (!). 
> 
> We use that already.  (Hmm, might be interesting for you to turn it
> *off* and see if anything changes.  See src/backend/port/sysv_shmem.c.)

Gah. Always must remember to RTFSource.
And reproduce the problem on a machine I control :-)

-- 
Engineers think that equations approximate reality.
Physicists think that reality approximates the equations.
Mathematicians never make the connection.

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