Re: Ick: Setting shared memory segment size (fwd)

Matthias Urlichs (smurf@work.smurf.noris.de)
5 Jan 1997 16:17:36 +0100

In linux.dev.kernel, article <9701011224.AA07157@halfpint.rtp.avanticorp.com>,
Jim Nance <jlnance@avanticorp.com> writes:
> >
> > You still need to reboot the machine for this to take effect. But I
> > agree it should be a /proc tunable if possible.
>
If itïs settable with /proc/whatever then there shouldnït be a need to
reboot.

> Just out of curisoity (no I cant spell), what forces there to be a limit
> on max shared mem sizes in the first place. I *THINK* that 2 processes
> can mmap() a file with MAP_SHARED and get any size of shared memory region
> that they want. If this is true, what is different about the shm*
> functions?
>
One reason is that if you mmap a file, the file is the place the system
swaps the memory to when it needs the room. With shm*, the memory gets
swapped out to swap, which the system can run out of rather easily.

-- 
In war, truth is the first casualty.
               --U Thant

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