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    SubjectRe: [PATCH] Patch to Memory Subsystem ... (Needed?)
    Riley Williams wrote:
    > Hi Brian.
    > >>> Now set the no. of freepages to say, 1024 (4 Mb on Intel
    > >>> platforms) and run 'eat' again as normal user. Watch the amount
    > >>> of free memory. It should drop down to ~ 4Mb - not below! You're
    > >>> then able to login as root and do your stuff ... ;o)
    > >> What if during the change there was less free pages than 1024?
    > >> (Sorry, too lazy to check the code)
    > > Then your *users* are in trouble - as I wrote later in the mail ;o)
    > > There's no check to see if 'rootpages' contains some strange or
    > > high value. But 'rootpages' doesn't affect UID 0 operations. Root
    > > *can* eat all memory if (s)he likes ...
    > > OTOH, rootpages is meant to be set during initialization of the
    > > system (like after /proc is mounted) ...........
    > Just a thought, but how much memory does root need to do suchlike
    > cleanups? Let's see - load the login shell (probably already in
    > memory anyway, so 0k), run ps (may already be in memory) to find out
    > which processes are currently hogging memory, then kill (usually a
    > shell internal, so 0k) to get rid of a few of them...that should do...

    Too many "propably's". If one of the "propably's" fail, you might end
    up in trouble - or so experience tell me.
    I ended up in trouble due to Linux being to kind to users
    malloc/calloc/*alloc requests. A lot of 'unable to load ...', 'cannot
    map blah, blah, blah' and the like.

    > OTOH, what happens if CRON or the like starts up a memory hog as root?
    > Surely those rootpages should be reserved for genuine logons,
    > otherwise the memory in question could easily be taken up by root
    > CRON jobs ???

    Absolutely correct. My sole intention is to keep my users from doing
    "anything stupid" (Ok, broad term!) If root asks for trouble, (s)he
    will get it!

    I don't see how (and maybe why) to implement something which would ban
    root from doing something "silly". Contribute that to my lack of
    knowledge with respect to the memory subsystem. I might have some
    ideas on how to implement a '5% Real Genuine Root-reserve', but I don't
    know what options the memory sub-system offers me or how flexible the
    mss is.

    I'll leave it to others (more proficient) to implement. Hint, hint!

    > Best wishes from Riley.

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