Guest page hinting patches.
Fourth version of the guest page hinting patches. The code has been polished and another race has been fixed (keep fingers crossed that is has been that last one this time).
The basic idea of guest page hinting is to give a host system which virtualizes the memory of its guest systems on a per page basis usage information for the guest pages. The host can then use this information to optimize the management of guest pages, in particular the paging. This optimizations can be used for unused (free) guest pages, for clean page cache pages, and for clean swap cache pages. The content of free pages can be replace with zeroes and the content of clean page cache / swap cache pages can be reloaded by the guest from the backing store.
There are 9 patches that implement guest page hinting:
1) Guest page state changes for free pages.
2) s390 exploitation of state changes for free pages.
3) Guest page state changes for page cache pages.
4) Guest page state changes for swap cache pages.
5) Keep mlocked pages in stable state.
6) Add support for writable page table entries.
7) Optimization for minor faults.
8) Discarded page list.
9) full s390 architecture support for guest page hinting.
The first two patches are independent from the other seven. These two just deal with unused/free vs. used/stable pages. The code starts to get interesting with patch #03..
Any objections against pushing patch #01 and patch #02 into the -mm tree?
The code runs well on s390 and does nothing for all other archs. Patches are against 2.6.18-rc4-mm2.
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Quoted 2 lines · Martin Schwidefsky
Any objections against pushing patch #01 and patch #02 into the -mm tree?
None from me. Although I'd rather put all that stuff (including kernel_map_page, as a cleanup) into arch_free_page and arch_alloc_page, rather than teaching core code about unstable pages just yet.
[BTW, if you do this, one actually notices that arch_free_page seems to be in the wrong place since the page reserved checks came into the allocator.]
Quoted 4 lines
The code runs well on s390 and does nothing for all other archs. Patches are against 2.6.18-rc4-mm2.
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Quoted 1 line · On Thu, 24 Aug 2006 16:29:11 +0200 Martin Schwidefsky <[email protected]>…
Fourth version of the guest page hinting patches.
The obvious question is: "can Xen/vmware/whatever use this too?". The preliminary answer I get back is "might well be the case". Hopefully we'll hear more back soon.
So a good way to get some monentum into this work is to copy [email protected] and lkml, try to get it some more users.
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