Date: Sun, 20 May 2012 09:01:32 +0200 From: Marko Zec <zec@fer.hr> To: <freebsd-hackers@freebsd.org> Cc: freebsd-amd64@freebsd.org Subject: superpages and kmem on amd64 Message-ID: <201205200901.32613.zec@fer.hr>
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Hi all, I'm playing with an algorithm which makes use of large contiguous blocks of kernel memory (ranging from 1M to 1G in size), so it would be nice if those could be somehow forcibly mapped to superpages. I was hoping that the VM system would automagically map (merge) contiguous 4k pages to superpages, but apparently it doesn't: vm.pmap.pdpe.demotions: 2 vm.pmap.pde.promotions: 543 vm.pmap.pde.p_failures: 266253 vm.pmap.pde.mappings: 0 vm.pmap.pde.demotions: 31 I.e. I have 1G of kmem allocated using via malloc(1024 * 1024 * 1024, M_TEMP, M_NOWAIT); but vm.pmap.pde.mappings: 0 suggests that no superpages are in use. Is there an alternative kernel memory allocation method which might force superpages to be used for contiguous memory blocks? And how do I find more details about page mappings for a given kmem virtual address? I'm running 8.3-STABLE on amd64. Thanks, Marko
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