Horton

Re: Shared Memory: How to use SYSV rather than MMAP ?

Peter Eisentraut <peter.eisentraut@2ndquadrant.com>

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From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: Thomas Munro <thomas.munro@enterprisedb.com>, Robert Haas <robertmhaas@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, "REIX, Tony" <tony.reix@atos.net>, Andres Freund <andres@anarazel.de>, Pg Hackers <pgsql-hackers@postgresql.org>, "EMPEREUR-MOT, SYLVIE" <sylvie.empereur-mot@atos.net>
Date: 2019-01-04T15:39:06Z
Lists: pgsql-hackers 
On 27/12/2018 00:53, Thomas Munro wrote:
> mmap and sysv were the same, but there
> did seem to be a measurable speed-up available at high client counts
> with kern.ipc.shm_use_phys=1 and thus for sysv only, for people
> prepared to set 3 sysctls and this proposed new GUC.  Maybe the effect
> would be greater with bigger shared_buffers or smaller pages (this
> test ran on super pages)?  More work required to figure that out.

Could you get a similar effect for mmap by using mlock() to prevent the
pages from being swapped?

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Add shared_memory_type GUC.

  2. Dramatically reduce System V shared memory consumption.