[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Regarding page table management changes from Xen v1to Xen v2 (and v3)
Ian Pratt wrote: In another example, mmapped access to a file, the new approach will incur these two extra faults for every page fault required to bring a file page to page cache, right?No, these singleton updates on the Linux demand fault path are issued with the update_va_mapping hypercall. This is possible because the virtual address that the pte maps is known, so its possible for Xen to use a linear pagetable to do the update rather than creating an on-demand mapping to the domain's pagetable page. This is an important optimization on 32b where Xen address space is tight. Just to make sure I understand, we do the linear mapping for performance (so we don't have to keep remapping) but not necessarily to save VA space since the linear mapping uses a fixed amount of space. Is there any reason that we would strictly require a linear mapping (other than it being convenient)? Thanks, Anthony Liguori Ian _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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