Messages in this thread | | | From | nathan.zook@amd ... | Subject | RE: bigmem questions | Date | Thu, 3 Feb 2000 13:26:46 -0600 |
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BTW, is the bigmem option incompatible with the nopentium command line option? (It disables 4M pages)
FTR, the Athlon currently supports 16G. BIOSES for the Athlon...don't. I don't know the K6 specs, but it was designed with PPro compatibility in mind.
Nathan Zook
> -----Original Message----- > From: Andrea Arcangeli [mailto:andrea@suse.de] > Sent: Wednesday, February 02, 2000 7:58 PM > To: Matt Chapman > Cc: linux-kernel@vger.rutgers.edu > Subject: Re: bigmem questions > > > On Wed, 2 Feb 2000, Matt Chapman wrote: > > >I have a couple of questions about the BIGMEM implementation. > > > >I understand BIGMEM will support up to 64G of physical RAM, but I > >haven't been able to glean from the postings what a user-process' > >virtual address space will be. [..] > > User-process virtual memory is physically limited to 4giga in the IA32 > architecture (unless you want to play dirty with segmentation > at least... > and you probably prefer to more cleanly use shm memory and attach and > deattach to shm segments or doing similar userspace non-IA32 specific > tricks to access the whole RAM). New PAE stuff won't help you on the > virtual memory side. > > Today you can use alpha with 2.2.14+bigmem patch if you need more RAM > per-task (is 2T enough for you? :). > > Due the kernel/user split on the virtual memory the usual limit for > linux-IA32 is around 2giga per-task (there are two one liner on my > ftp-area to increase it to 3.5g per-task though). > > >[..] The SGI and SuSE patches that I've > >seen map almost 4G virtual into physical RAM. Does BIGMEM support > >this range or will it retain the old 3G virtual space? > > NOTE: when you talk about the SuSE patches you are exactly > talking about > BIGMEM. FYI: BIGMEM is been originally designed and developed > from scratch > by me at SuSE and Gerhard Wichert at Siemens. > > The BIGMEM SuSE patches that broken the 2giga RAM limit on > IA32 are been > included into 2.3.16. Then during 2.3.x the patch that did > the rest of the > stuff necessary for >4g support (so implementing the three level > pagetables of PAE mode and changing GFP to return a struct > page * instead > of a 32bit interger) also renamed the word "bigmem" to "highmem". > > (BTW, personally I prefer the original "bigmem" name for the > thing, and > the rename just generated confusion to you for example.) > > >Does BIGMEM adjust to the amount of RAM installed? For example, the > >2.2.x release requires one kernel build for less than 1G and another > >for over 1G. Will BIGMEM support say 16M to 64G with the same kernel > >build? > > You can support more than 4giga only on P6 chips, a kernel > compiled for > supporting 64giga of ram won't run on older IA32 chips like the P5 > generation, I actually don't know about AMD and others. > Probably we should > put a dependency for PAE mode on P6 compile. > > If you compile without PAE (so with 4G support) the resulting > kernel will > run all over the place. > > >How about support for 16M to 4G RAM with one kernel? > > Fine. You can just do it with 2.2.14+bigmem btw. > > >If rebuilding is required, why? [..] > > Not required. > > > [..] Is there a sizable performance hit in > >making it dynamic? > > No. > > Andrea > > > - > To unsubscribe from this list: send the line "unsubscribe > linux-kernel" in > the body of a message to majordomo@vger.rutgers.edu > Please read the FAQ at http://www.tux.org/lkml/ >
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