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Re: Solaris ISM Testing

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "P(dot)J(dot) \"Josh\" Rovero" <rovero(at)sonalysts(dot)com>,PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Solaris ISM Testing
Date: 2002-02-22 05:52:59
Message-ID: 200202220552.g1M5qxC27517@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > The attached email shows that Solaris benefits from the ISM or Intimate
> > Shared Memory setting during shmat() shared memory creation.  It causes
> > processes mapping the same shared memory to shared mapping pages _and_
> > locks the pages in RAM.
> 
> Huh?  I understand "locks the pages in RAM" but I don't understand the
> first part of that.  ISTM shared memory is shared memory; if we didn't
> share it without this flag, we'd not be working at all on Solaris.

It shares the virtual page map tables as well as the actual RAM pages.

> > I know many OS's lock shared memory in RAM anyway, or have OS parameters
> > that control this (FreeBSD), but it seems Solaris does this on a per
> > shmat() basis.  Should we add this flag to shmat() calls for Solaris?
> 
> Certainly on any OS where we can request pinning our shmem in RAM, we
> should do so --- I've pointed out before that allowing our disk buffers
> to be swapped out can't be anything but counterproductive.  Not sure
> that this should be thought of as an "#ifdef SOLARIS" kind of change;
> do any other Unixen share this aspect of the API?

Yes, #ifdef SOLARIS.  I am waiting from a patch from the reporter.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

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