Re: First set of OSDL Shared Mem scalability results, some - Mailing list pgsql-performance

From Tom Lane
Subject Re: First set of OSDL Shared Mem scalability results, some
Date
Msg-id 29890.1098667087@sss.pgh.pa.us
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In response to Re: First set of OSDL Shared Mem scalability results, some  (Curt Sampson <cjs@cynic.net>)
Responses Re: First set of OSDL Shared Mem scalability results, some  (Curt Sampson <cjs@cynic.net>)
List pgsql-performance
Curt Sampson <cjs@cynic.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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