[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-ia64-devel] Virtual mem map
Le Vendredi 06 Janvier 2006 22:40, Magenheimer, Dan (HP Labs Fort Collins) a écrit : > > I am currently thinking about virtual mem map. > > In Linux, the virtual mem map is (surprise) virtually mapped. > > In Xen, we can use the same approach or we can manually cut > > the mem map into > > several pieces using a mechanism similar to paging. [...] > I think you will need to explain a little bit more what you > mean by "a mechanism similar to paging" before it will > be possible to comment. Paging, to me, means there is some > kind of swap drive or backing store to allow more "virtual" > pages than "physical" pages. [I have just describe it in my previous mail]. > I spent a lot of time recently digging through the physical > memory management code of Linux/ia64. It is very messy because > it has to support a wide variety of physical memory layouts. > And it makes surprising choices that throw away huge chunks of > physical memory (anything that doesn't fit conveniently in > a "granule"). Yes, this is very surprising. At least 16MB of memory are lost! Maybe Xen can use this memory for itself ? > Getting this all working on multiple machines > will probably be a big challenge. It might be best to use > Linux code that is known to work on many machines. Sure. On the other side, Xen (almost) don't use ptc/itc for itself. > I agree with your concern though that taking TLB misses when > looking up a page struct in Xen is likely to cause performance > problems and some difficult bugs. It might be worthwhile to > put some counters in to see how frequently the memmap is > accessed and code some defensive bounds checks to ensure > wild accesses are immediately flagged with a BUG rather than > resulting in random memory accesses. I agree. Tristan. _______________________________________________ Xen-ia64-devel mailing list Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-ia64-devel
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