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Quote from Helge Hafting <helgehaf@aitel.hist.no>: > Anthony DiSante wrote: > > > As a general question about ram/swap and relating to some of the > > issues in this thread: > > > > ~500 megs cached yet 2.6.5 goes into swap hell > > > > Consider this: I have a desktop system with 256MB ram, so I make a > > 256MB swap partition. So I have 512MB "memory" and if some process > > wants more, too bad, there is no more. > > > > Now I buy another 256MB of ram, so I have 512MB of real memory. Why > > not just disable my swap completely now? I won't have increased my > > memory's size at all, but won't I have increased its performance lots? > > This is correct. You now have 512M of fast memory instead of > 256M fast memory and 256M "slow" memory. You don't _need_ to have additional > swap, but it is usually a good idea. If you keep your 256M of swap, > then you now > have 512M fast memory + 256M slow memory for a total of 768M. This is > even better. I strongly disagree on the last point. It may be better, but it may also be a lot worse. Too much swap can be a bad thing - see my example in another post about run-away processes on remote machines. > Please note that your machine _will_ do one kind of swapping even if you > don't configure any swap: Executable files are a kind of swap-files, > if memory pressure happens then (part of) your programs will be evicted > from memory _because_ they can be reloaded from their executables. > > This cause the same sort of performance degradations as swapping to > a swap partition. Actually, it is worse because swapping to a swap > partition > allows swapping out little-used writeable memory before discarding > program code that might see more use. So if swapping happens, then > you're better off with a swap partition because then it is the least used > stuff that goes first. Without a swap partition, the least used program code > goes, but it may or may not be the least used memory overall. Again, the user _may_ be better off swapping to a swap partition rather than having executable code paged out, but this is not necessarily true in all circumstances. John. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | |||||||||
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