I believe shmmax is a limit, preventing a single process from using more more than this. This sounds like it's essentially unlimited. There's no performance impact, unless the sum of all shared mem (see ipcs) becomes significant and performance degrades. On the other hand, if a lower limit is set and an application requires more shared mem than allowed by shmmax, the allocation (and application) would fail, which can be very undesirable.
Limiting shmmax might limit swapping indirectly, by inhibiting the operation of processes (via failure). I think it would be better to manage system load in other ways. Cheers, -Bob Arendt On 11/05/09 00:43, Corey Kovacs wrote:
Looking at some 64 bit machines I have running RHEL5.4, I noticed that the shmmax settings in sysctl.conf are getting set to 64GB. The machines only have from 16 to 32GB. Is this normal on a 64bit load? Seems like a good way to end up swapping. Corey
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