[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-ia64-devel] Virtual mem map
>From: Tristan Gingold >Sent: 2006年1月6日 20:58 >Hi, > >I am currently thinking about virtual mem map. >In Linux, the virtual mem map is (surprise) virtually mapped. Surprised but efficient and necessary. ;-) >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'm not exactly catching your meaning here. In case of physical memmap, identity mapped va is used and thus no special track structures (meaning pgtable in Linux) required. When physical memmap is converted to virtual memmap, it means you have to provide a virtually contiguous area to be mapped to an array of physical incontinuous pages, and thus you need extra PTEs in pgtable. So in both cases you mentioned, extra structure to track mapping is necessary. Maybe the difference is that you propose to use another simpler structure (like a simple array/list) instead of multi-level page table? And then modify all memmap related macros (like pfn_valid, page_to_pfn, etc) to let them know existence of holes within memmap? > >I don't really like the first way: this uses TLB, this may causes more >troubles and currently Xen almost don't use translation cache for itself. > >So, I think I will use the second approach. So you really need to elaborate your 2nd approach with the exact difference provided. Actually more questions come with this issue: Do we need to add generic non-identity mapping into Xen? If yes, then there's no special think for virtual memmap which can be covered. If no, we already saw some limitation upon lacking of such feature, which can't manage/utilize machine page frames efficiently. If yes, we may need add multi-level page table into Xen and walk it in page fault handler. Then do we need VHPT table for Xen for performance? Currently all vhpt tables are only for guest running... When we're working around one specific issue, I hope the solution can be more generic to cover future similar requirement. Thanks, Kevin > >Am I missing an important point ? >Am I doing the wrong choice ? >Please, comment. > >Tristan. > > >_______________________________________________ >Xen-ia64-devel mailing list >Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx >http://lists.xensource.com/xen-ia64-devel _______________________________________________ Xen-ia64-devel mailing list Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-ia64-devel
|
![]() |
Lists.xenproject.org is hosted with RackSpace, monitoring our |