Date: Sun, 20 Feb 2000 22:20:24 -0800 From: Arun Sharma <adsharma@c62443-a.frmt1.sfba.home.com> To: dillon@apollo.backplane.com Cc: freebsd-hackers@freebsd.org Subject: Re: 64bit OS? Message-ID: <200002210620.WAA27921@c62443-a.frmt1.sfba.home.com> In-Reply-To: <200002200653.WAA99167@apollo.backplane.com> References: <200002200528.QAA04257@mycenae.ilion.eu.org> <200002200653.WAA99167@apollo.backplane.com>
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Matt Dillon wrote: > > Linux also stores persistent information in their machine independant > page tables. They aren't throw-away like FreeBSD's are. This will give > us a huge advantage when we do the IA64 port. I forgot to mention that Linux/IA-64 switches the processor to physical mode to walk the 3 level page table in the VHPT miss handler. This has additional overheads associated. > In general I like the idea of using a VHPT as an STLB (are we having > fun with terminology yet?). Yes, Software TLB is a misnomer. Second level TLB is probably better. VHPT can behave as either STLB or the primary page table of the OS. > What I would truely love to do would be to get away with not using a GPT > at all and instead doing a vm_map_lookup_entry()/vm_page_lookup() > (essentially taking a vm_fault), then optimize the vm_map_entry > structural hierarchy to look more like a GPT rather then the linear > list it currently is. When coupled with an STLB, especially one that > can be optimized, I think performance would be extremely good. For finding the vm_map_entry for a virtual address, a balanced binary tree works better. Linux does well here - it uses AVL trees, which find the right vm_map_entry in O(log n) time. -Arun To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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