Date: Tue, 5 Aug 2008 10:24:25 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-arch@freebsd.org Cc: Nathan Whitehorn <nwhitehorn@freebsd.org> Subject: Re: UMA MD Small Allocator Runtime Switching Message-ID: <200808051024.27043.jhb@freebsd.org> In-Reply-To: <48981C19.8060009@freebsd.org> References: <48981C19.8060009@freebsd.org>
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On Tuesday 05 August 2008 05:23:37 am Nathan Whitehorn wrote: > I'm working on the PowerPC G5 port right now, and have run into a > problem with the way the UMA small allocator works. On G3/G4 systems, > there is a direct physical->virtual mapping, and on G5s there isn't. All > of the infrastructure is in place to support both types of system with a > single kernel image, except that UMA_MD_SMALL_ALLOC must be switched > on/off at runtime. > > One solution is to put if (direct_map) use_nonsmall_case() into the MD > small_alloc/free() routines and define UMA_MD_SMALL_ALLOC everywhere. > This works well, except that the MI UMA code then sets booted = 1 too > early in the boot process, before the kmem_alloc*() routines are available. > > Basically, I need to find a way have an MD UMA allocator without the MI > UMA code assuming anything about how it works internally. Maybe adding a > UMA_MD_ALLOC_LATE define to prevent setting booted=1 early on? > -Nathan Have you considered creating an artificial direct map region in the address space on the G5? Some of the other 64-bit ports (amd64 and sparc64) do this to gain the benefits of the direct map even though it isn't a mandated part of the architecture like it is on some other platforms (alpha and mips). -- John Baldwin
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