Dave Hansen wrote: > On Fri, 2009-03-27 at 16:09 +0100, Martin Schwidefsky wrote: >> If the host picks one of the >> pages the guest can recreate, the host can throw it away instead of writing >> it to the paging device. Simple and elegant. > > Heh, simple and elegant for the hypervisor. But I'm not sure I'm going > to call *anything* that requires a new CPU instruction elegant. ;) I am convinced that it could be done with a guest-writable "bitmap", with 2 bits per page. That would make this scheme useful for KVM, too. > I don't see any description of it in there any more, but I thought this > entire patch set was to get rid of the idiotic triple I/Os in the > following scenario: > I don't see that mentioned at all in the current description. > Simplifying the hypervisor is hard to get behind, but cutting system I/O > by 2/3 is a much nicer benefit for 1200 lines of invasive code. ;) Cutting down on a fair bit of IO is absolutely worth 1200 lines of fairly well isolated code. > Can we persuade the hypervisor to tell us which pages it decided to page > out and just skip those when we're scanning the LRU? The easiest "notification" points are in the page fault handler and the page cache lookup code. -- All rights reversed. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
