On Fri, 24 Mar 2000, David Whysong wrote:
> On Fri, 24 Mar 2000, Marco Colombo wrote:
> >On 22 Mar 2000, Olaf Weber wrote:
>
> >No problem. Is is problem that your program gets stoppen when it gets
> >SIGTSTP? If no, you don't have to use any "special programming techniques".
> >If yes, you may think of trapping the signal and inform the user that
> >stopping your application is not possible. Are you concerned of your
> >program being killed at OOM time? Use special techniques to avoid
> >triggering the OOM killer (i.e., do not page-fault). It's harder
> >than just using signal(), i admit it. It may also be impossible to do
> >in a really "safe" way (your stack may grow...).
>
> It's completely impossible to avoid a page fault (as it should be). You
> page fault, if (for example) the kernel has swapped out your data, or
> dropped your executable pages on the floor, it will later need to read
> them back into memory.
>
> Yes, mlock() solves this, but only root can mlock(). That's not a good
> solution for users.
For users you use resource limits to stop them *before* they reach OSS.
We were discussing sophisticated applications which need to take control
over mm of their address space. No bad you need root permissions to do that.
> >IFAIK, older linux versions had no overcommitting. The kernel *evolved*
> >from a non-overcommitting mm to a overcommitting one.
>
> No, it has overcommitted memory almost since the beginning. These comments
> are from linux 1.0.0, in mm/memory.c. Note the dates:
>
> /*
> * demand-loading started 01.12.91 - seems it is high on the list of
> * things wanted, and it should be easy to implement. - Linus
> */
>
> /*
> * Ok, demand-loading was easy, shared pages a little bit tricker. Shared
> * pages started 02.12.91, seems to work. - Linus.
> *
> * Tested sharing by executing about 30 /bin/sh: under the old kernel it
> * would have taken more than the 6M I have free, but it worked well as
> * far as I could see.
> *
> * Also corrected some "invalidate()"s - I wasn't doing enough of them.
> */
I don't think the above comment is about overcommitting swap space.
He's talking about sharing the text segments of processes, i think.
But you should ask Linus, I was not there at the moment (01.12.91) B-).
>
>
> Dave
>
> David Whysong dwhysong@physics.ucsb.edu
> Astrophysics graduate student University of California, Santa Barbara
> My public PGP keys are on my web page - http://www.physics.ucsb.edu/~dwhysong
> DSS PGP Key 0x903F5BD6 : FE78 91FE 4508 106F 7C88 1706 B792 6995 903F 5BD6
> D-H PGP key 0x5DAB0F91 : BC33 0F36 FCCD E72C 441F 663A 72ED 7FB7 5DAB 0F91
>
>
.TM.
--
____/ ____/ /
/ / / Marco Colombo
___/ ___ / / Technical Manager
/ / / ESI s.r.l.
_____/ _____/ _/ Colombo@ESI.it
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