Looking at the 2.0 code, it looks like the guest OSs are made to believe that PSE is not available. Is this a design choice? Has any work been done on supporting 4M pages in guest kernels? Regards, K. Y ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ Xen-devel mailing list Xen-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/xen-devel
One issue that Ian would tell is that the linear page table technique frequently used by Xen would (when accessing PTE) be broken because the PS Bit (Bit 7) in a page-directory entry becomes PAT Bit (Bit 7) in the page-table entry. We are considering supporting 2MB and 4MB pages in shadow mode (especially for VMX domains). Jun -----Original Message----- From: xen-devel-admin@lists.sourceforge.net [mailto:xen-devel-admin@lists.sourceforge.net] On Behalf Of Ky Srinivasan Sent: Tuesday, February 22, 2005 5:12 PM To: xen-devel@lists.sourceforge.net Subject: [Xen-devel] PSE in guests Looking at the 2.0 code, it looks like the guest OSs are made to believe that PSE is not available. Is this a design choice? Has any work been done on supporting 4M pages in guest kernels? Regards, K. Y ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ Xen-devel mailing list Xen-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/xen-devel ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_ide95&alloc_id396&op=click _______________________________________________ Xen-devel mailing list Xen-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/xen-devel
> Looking at the 2.0 code, it looks like the guest OSs are made to > believe that PSE is not available. Is this a design choice? > Has any work been done on supporting 4M pages in guest kernels?We did some experiments using 4M pages to map the kernel, but didn''t get any speedup as recorded by lmbench. We''d like to get hugetlbfs working so that databases can use it at some point, but it''s a bit subtle: Xen uses linear (recursive) pagetables internally for performance reasons, and the dumb x86 page table format means that its not possible to cause a fault to occur if an attempt is made to use a super page entry in the PGD as a PTE (as a result of the recursive map). We''ll need to add secondary checks :-( Ian ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_ide95&alloc_id396&op=click _______________________________________________ Xen-devel mailing list Xen-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/xen-devel