Anthony Liguori wrote: > Avi Kivity wrote: > >> Anthony Liguori wrote: >> >> >>> Now that we have userspace memory allocation, I wanted to play with >>> ballooning. >>> The idea is that when a guest "balloons" down, we simply unpin the >>> underlying >>> physical memory and the host kernel may or may not swap it. To reclaim >>> ballooned memory, the guest can just start using it and we'll pin it on >>> demand. >>> >>> The following patch is a stab at providing the right infrastructure for >>> pinning >>> and automatic repinning. I don't have a lot of comfort in the MMU code so I >>> thought I'd get some feedback before going much further. >>> >>> gpa_to_hpa is a little awkward to hook, but it seems like the right place >>> in the >>> code. I'm most uncertain about the SMP safety of the unpinning. >>> Presumably, >>> I have to hold the kvm lock around the mmu_unshadow and page_cache release >>> to >>> ensure that another VCPU doesn't fault the page back in after mmu_unshadow? >>> >>> >>> >>> >> One we have true swapping capabilities (which imply ability for the >> kernel to remove a page from the shadow page tables) you can unpin by >> calling munmap() or madvise(MADV_REMOVE) on the pages to be unpinned. >> >> > > So does MADV_REMOVE remove the backing page but still allow for memory > to be faulted in? That is, after calling MADV_REMOVE, there's no > guarantee that the contents of a give VA range will remain the same (but > it won't SEGV the app if it accesses that memory)? > >
I think so. The docs aren't clear. See also MADV_DONTNEED. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
