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Re: First set of OSDL Shared Mem scalability results, some

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Curt Sampson <cjs(at)cynic(dot)net>
Cc: Kevin Brown <kevin(at)sysexperts(dot)com>,pgsql-performance(at)postgresql(dot)org
Subject: Re: First set of OSDL Shared Mem scalability results, some
Date: 2004-10-25 01:18:07
Message-ID: 29890.1098667087@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
Curt Sampson <cjs(at)cynic(dot)net> writes:
> I see the OS issues related to mapping that much memory as a much bigger
> potential problem.

I see potential problems everywhere I look ;-)

Considering that the available numbers suggest we could win just a few
percent (and that's assuming that all this extra mechanism has zero
cost), I can't believe that the project is worth spending manpower on.
There is a lot of much more attractive fruit hanging at lower levels.
The bitmap-indexing stuff that was recently being discussed, for
instance, would certainly take less effort than this; it would create
no new portability issues; and at least for the queries where it helps,
it could offer integer-multiple speedups, not percentage points.

My engineering professors taught me that you put large effort where you
have a chance at large rewards.  Converting PG to mmap doesn't seem to
meet that test, even if I believed it would work.

			regards, tom lane

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