On Wed, Aug 27, 2008 at 02:45:47PM -0700, david@xxxxxxx wrote: > with memory overcommit enabled (the default), the kernel recognises that > most programs that fork don't write to all the memory they have > allocated, It doesn't "recognise" it; it "hopes" it. It happens to hope correctly in many cases, because you're quite right that many programs don't actually need all the memory they allocate. But there's nothing about the allocation that hints, "By the way, I'm not really planning to use this." Also. . . > seperate copies for the seperate processes (and if at this time it runs of > of memory it invokes the OOM killer to free some space), . . .it kills processes that are using a lot of memory. Those are not necessarily the processes that are allocating memory they don't need. The upshot of this is that postgres tends to be a big target for the OOM killer, with seriously bad effects to your database. So for good Postgres operation, you want to run on a machine with the OOM killer disabled. A -- Andrew Sullivan ajs@xxxxxxxxxxxxxxxxx +1 503 667 4564 x104 http://www.commandprompt.com/
