Matija Nalis wrote:
>
> On 17 Mar 2000 00:27:42 +0100, Rask Ingemann Lambertsen <rask-linux@kampsax.k-net.dk> wrote:
> >Den 15-Mar-00 11:49:45 skrev James Sutherland følgende om "Re: Overcommitable memory??":
> >> On Wed, 15 Mar 2000, David Whysong wrote:
> >
> >>> The only possibilities are to (a) enforce hard memory limits with no
> >>> overcommit, thereby wasting large amounts of swap space that will never
> >>> get used while not really solving the problem,
> >
> >> As well as *destroying* performance (you'd effectively eliminate COW
> >> capability on fork - if your 500Mb simulation wants to fork a 100k mailer
> >> process to send you an update, the kernel has to allocate and copy 500Mb
> >> of RAM/swap first, then discard it all again.)
> >
> > Not at all. COW is a performance optimisation which does not depend on
> >overcommitment of memory in any way. Why would you want to turn it off?
>
> Say you have 800MB virtual RAM, and you simulation currently uses 500MB.
> And now, it tries to fork(2). Do you allow it, or does fork fail with
> -ENOMEM ?
--- Had exactly this problem in SoftWindows on IRIX. It would fork to run some trivial external application, or a sound-process. It would die running out of memory (SWin mem image was often large). Solution was to convert to using 'sproc', where amount of process sharing can be user defined -- something like a heavy-weight thread. If all you were going to do was to exec another proc, you could set the new proc to "share all mem": PR_SADDR All virtual space attributes (shared memory, mapped files, data space) are shared. If one process in a share group attaches to a shared memory segment, all processes in the group can access that segment. == Then do the exec call. Thus no overcommit. -l -- Linda A Walsh | Trust Technology, Core Linux, SGI law@sgi.com | Voice: (650) 933-5338- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Thu Mar 23 2000 - 21:00:25 EST