Date: Thu, 29 Jul 2010 12:06:32 -0500 From: Alan Cox <alc@cs.rice.edu> To: Jeff Roberson <jroberson@jroberson.net> Cc: svn-src-projects@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r210586 - projects/ofed/head/sys/ofed/include/linux Message-ID: <4C51B518.8060607@cs.rice.edu> In-Reply-To: <alpine.BSF.2.00.1007282303220.1414@desktop> References: <201007290212.o6T2CN20099343@svn.freebsd.org> <4C50FB4A.4000505@cs.rice.edu> <alpine.BSF.2.00.1007282303220.1414@desktop>
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Jeff Roberson wrote: > On Wed, 28 Jul 2010, Alan Cox wrote: > >> Jeff Roberson wrote: >>> Author: jeff >>> Date: Thu Jul 29 02:12:22 2010 >>> New Revision: 210586 >>> URL: http://svn.freebsd.org/changeset/base/210586 >>> >>> Log: >>> - Refine various page allocation methods. They all essentially >>> override >>> the page object pointer to cache the virtual address after >>> allocation. >>> This same trick is used in UMA to store the slab address and so it >>> should be safe. >>> >> >> You needn't do this. The virtual address of a kernel_object or >> kmem_object page is easily obtained: >> >> VM_MIN_KERNEL_ADDRESS + IDX_TO_OFF(m->pindex) > > Ah, of course. I hadn't considered that. Thanks. I'll remove the > other hackery. > > On another note; linux guarantees multipage allocations are aligned on > the first power of two size that satisfies the allocation. I can do > this with contigmalloc but they also guarantee that the virtual > address is similarly aligned. I don't think I've run across anything > that requires it, but if I do, do we have any provision for allocating > virtually aligned addresses? > No, I'm afraid not. We only support a couple of specific cases of virtually aligned allocation: thread stacks on MIPS and the start of the large submaps on superpage-enabled architectures. Alan
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