Hi! > > >>>I have (had?) code that 'exploits' this. I believe I could eat 90% of cpu > >>>without being noticed. > >> > >>Slightly changed version of hog(around 3 lines in total changed) does that > >>easily on 2.6.18.3 on PPC. > >> > >>http://www.boblycat.org/~malc/apc/load-hog-ppc.png > > > >I guess it's worth mentioning this is _only_ about displaying the cpu > >usage to > >userspace, as the cpu scheduler knows the accounting of each task in > >different ways. This behaviour can not be used to exploit the cpu scheduler > >into a starvation situation. Using the discrete per process accounting to > >accumulate the displayed values to userspace would fix this problem, but > >would be expensive. > > Guess you are right, but, once again, the problem is not so much about > fooling the system to do something or other, but confusing the user: > > a. Everything is fine - the load is 0%, the fact that the system is > overheating and/or that some processes do not do as much as they > could is probably due to the bad hardware. > > b. The weird load pattern must be the result of bugs in my code. > (And then a whole lot of time/effort is poured into fixing the > problem which is simply not there) > > The current situation ought to be documented. Better yet some flag > can
It probably _is_ documented, somewhere :-). If you find nice place where to document it (top manpage?) go ahead with the patch. > be introduced somewhere in the system so that it exports realy values to > /proc, not the estimations that are innacurate in some cases (like hog) Patch would be welcome, but I do not think it will be easy. -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
