On Sat, Feb 02, 2008 at 09:49:05PM +0100, Florian G. Pflug wrote: > AFAICS, memory overcommit helps if a program creates 50mb of mosty > read-only data, and than forks 10 times, or if it maps a large amount of > memory but writes to that block only sparsely. Since postgres does > neither, a dedicated postgres server won't see any benefits from > overcommitting memory I'd think.
While this was probably intented to be funny, postgres does in fact load 10mb of mostly read-only data (the binary/libc/ssl/locales/kerberos add up to about 10mb on my machine) it subsequently forks a dozen times, one for each connection. So postgres is *exactly* such a program. If you start preloading plperl/plpython/etc it grows even faster. Now, postgres almost certainly will never change much of it so it's not a big deal, but it could if it wanted to and that what overcommit was designed for: banking on the fact that 99% of the time, that space isn't written to. Overcommit is precisely what makes forking as cheap as threads. Have a nice day, -- Martijn van Oosterhout <[EMAIL PROTECTED]> http://svana.org/kleptog/ > Those who make peaceful revolution impossible will make violent revolution > inevitable. > -- John F Kennedy
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