Messages in this thread | | | Date | Fri, 06 Nov 1998 21:18:25 +0100 | From | Brian Schau <> | Subject | Re: [PATCH] Patch to Memory Subsystem ... (Needed?) |
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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 libc.so. 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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