Date: Mon, 29 Nov 2010 10:46:18 -0600 From: Alan Cox <alc@rice.edu> To: John Baldwin <jhb@freebsd.org> Cc: alc@freebsd.org, freebsd-current@freebsd.org, Sean Bruno <seanbru@yahoo-inc.com> Subject: Re: 40 vs 44 bit memory addressing HP DL580/980 Message-ID: <4CF3D8DA.4050308@rice.edu> In-Reply-To: <201011290945.35128.jhb@freebsd.org> References: <1290387926.16558.1283.camel@home-yahoo> <201011221447.13026.jhb@freebsd.org> <4CEB126E.2010509@rice.edu> <201011290945.35128.jhb@freebsd.org>
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John Baldwin wrote: > On Monday, November 22, 2010 8:01:34 pm Alan Cox wrote: > >> On 11/22/2010 1:47 PM, John Baldwin wrote: >> >>> On Monday, November 22, 2010 1:37:45 pm Alan Cox wrote: >>> >>>> On Mon, Nov 22, 2010 at 6:59 AM, John Baldwin<jhb@freebsd.org> wrote: >>>> >>>> >>>>> On Sunday, November 21, 2010 8:05:26 pm Sean Bruno wrote: >>>>> >>>>>> Looks like these HP boxes have the capability to do 44 bit memory >>>>>> addressing if configured to do so from the BIOS. >>>>>> >>>>>> Is anyone interested in any data from that setting? >>>>>> >>>>> Does it boot ok? :) The MTRR code should handle that (there is a CPUID >>>>> field that tells the OS how many bits are significant). Not sure if there >>>>> are any places in the pmap that assume 40 bits, but a test boot is >>>>> certainly >>>>> worth trying. >>>>> >>>>> >>>>> >>>> Since we don't boot with 40-bit addressing, I can easily predict the >>>> outcome. :-) >>>> >>>> The trouble with this machine is that the second 128GB of RAM is being >>>> placed between 512G and 1T in the physical address space, which is beyond >>>> the range of the (current) direct map. So, we take a page fault on the >>>> first access to a page in the second 128GB through the direct map. >>>> >>> Heh, I guess that is what your earlier patch did? Once that patch is applied >>> I think Sean should just try 44-bit mode if so. >>> >>> >> Yes. >> >> If 44-bit addressing makes the placement of DRAM in the physical address >> space any sparser, then we'll again have an insufficiently large direct >> map. Also, I fear that we won't be able to allocate the vm_page_array >> without enabling VM_PHYSSEG_SPARSE, which itself requires a change in >> order to work. >> > > I believe someone has a change for that on amd64 already? > > Yes. Alan
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