Date: Mon, 07 Jun 2010 16:29:27 -0500 From: Alan Cox <alc@cs.rice.edu> To: Kostik Belousov <kostikbel@gmail.com> Cc: "Jayachandran C." <jchandra@freebsd.org>, mips@freebsd.org Subject: Re: svn commit: r208589 - head/sys/mips/mips Message-ID: <4C0D64B7.7060604@cs.rice.edu> In-Reply-To: <20100607202844.GU83316@deviant.kiev.zoral.com.ua> References: <AANLkTimIa3jmBPMhWIOcY6DenGpZ2ZYmqwDTWspVx0-u@mail.gmail.com> <AANLkTil2gE1niUWCHnsTlQvibhxBh7QYwD0TTWo0rj5c@mail.gmail.com> <AANLkTinA2D5iTDGPbflHVzLyAZW-ZewjJkUWWL8FVskr@mail.gmail.com> <4C07E07B.9060802@cs.rice.edu> <AANLkTimjyPc_AXKP1yaJaF1BN7CAGBeNikVzcp9OCb4P@mail.gmail.com> <4C09345F.9040300@cs.rice.edu> <AANLkTinmFOZY3OlaoKStxlNIRBt2G2I4ILkQ1P0CjozG@mail.gmail.com> <4C0D2BEA.6060103@cs.rice.edu> <AANLkTikZxx_30H9geHvZYkYd0sE-wiuZljEd0PAi14ca@mail.gmail.com> <4C0D3F40.2070101@cs.rice.edu> <20100607202844.GU83316@deviant.kiev.zoral.com.ua>
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On 6/7/2010 3:28 PM, Kostik Belousov wrote: > Selecting a random message in the thread to ask my question. > Is the issue that page table pages should be allocated from the specific > physical region of the memory ? If yes, doesn't i386 PAE has similar > issue with page directory pointer table ? I see a KASSERT in i386 > pmap that verifies that the allocated table is below 4G, but I do not > understand how uma ensures the constraint (I suspect that it does not). > For i386 PAE, the UMA backend allocator uses kmem_alloc_contig() to ensure that the memory is below 4G. The crucial difference between i386 PAE and MIPS is that for i386 PAE only the top-level table needs to be below a specific address threshold. Moreover, this level is allocated in a place, pmap_pinit(), where we are allowed to sleep. Alan
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