From: | The Hermit Hacker <scrappy(at)hub(dot)org> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | t-ishii(at)sra(dot)co(dot)jp, "Daryl W(dot) Dunbar" <daryl(at)www(dot)com>, pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: [HACKERS] PostgreSQL and Solaris 7? |
Date: | 1999-02-11 19:07:45 |
Message-ID: | Pine.BSF.4.05.9902111507140.13898-100000@thelab.hub.org |
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Thread: | |
Lists: | pgsql-hackers |
As promised, sorry for the delay...
http://sunsolve.Sun.COM/private-cgi/us/doc2html?infodoc/2270+91876015215168
This gives an explnation of it all for Solaris...
On Thu, 11 Feb 1999, Tom Lane wrote:
> Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp> writes:
> > Ok. If I consider 64 backends, at least following settings would be
> > required from your suggestion:
>
> > 64 entries in semaphore map (SEMMAP)
> > 64 semaphore identifiers (SEMMNI)
> > 64 semaphores in system (SEMMNS)
> > 25 max semaphores per id (SEMMSL)
>
> > Is this correct?
>
> No. You do need SEMMNS >= 64 of course, but Postgres only needs a
> sema identifier for each block of 16 semas, so SEMMNI >= 4 will work.
> According to my references, the recommended value of SEMMAP is SEMMNI+2
> (it's for keeping track of unused "holes" between allocated sema-ID
> groups, so that seems like it ought to be enough). SEMMSL could be as
> low as 16, though I see no reason to reduce the default value.
>
> In reality, of course, you had better leave some slop for other Unix
> programs to be able to grab semas of their own. I'd suggest at least
> doubling the minimum SEMMNS and SEMMNI. (On my HP box, ipcs shows
> various root-owned subsystems using 6 sema IDs with a total of 8 semas.
> So I'd need at least SEMMNS = 72, SEMMNI = 10 to run 64 backends ---
> with no margin for error.)
>
> I never understood why the default sema configuration values were so
> small anyway --- it's not like a semaphore uses a huge amount of kernel
> space...
>
> regards, tom lane
>
Marc G. Fournier
Systems Administrator @ hub.org
primary: scrappy(at)hub(dot)org secondary: scrappy(at){freebsd|postgresql}.org
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