Messages in this thread |  | | Date | Sun, 11 Nov 2001 22:33:31 +0000 | From | Mark Zealey <> | Subject | Re: Best kernel config for exactly 1GB ram |
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On Sun, Nov 11, 2001 at 02:56:58PM -0600, Steve Bergman wrote:
> Hi, > > > I have just upgraded my athlon 1200 system to 1GB ram. I am unclear as > to how I should configure the kernel for this box. The config.help says > to say no to "high memory support" if the kernel will not run on a > machne with more than 1GB. When I do this I notice that my available > memory as reported by top is ~ 120MB less than if I say I want 4GB > support. I recall that linux reserves some of the address space for > itself (I thought it was just 64MB). > > What are the trade offs involved here? Am I better off sacrificing a > bit of the physical memory for reasons of efficiency elsewhere? When I > request support for up to 4GB, what exactly changes with respect to the > visible virtual address space that apps see, etc? > > This is a desktop machine, so it's not running Oracle or anything like > that. I seem to recall Linus mentioning that big databases tend to like > the large (3GB) virtual address space.
Personally, I'd just leave it at the default no high-mem option.
The kernel will then be able to 'see' about 960MB of the memory, so you loose about 64MB of it, but it's not worth the kernel using bounce-buffers etc just so you can get 64MB more memory.
IIRC there was a 2GB patch that just redefined PAGE_OFFSET or something similar, this means that you could see all the memory, but the max virtual memory a process could see would be 2 gig (as opposed to 3 gig with the default).
--
Mark Zealey mark@zealos.org mark@itsolve.co.uk
UL++++>$ G!>(GCM/GCS/GS/GM) dpu? s:-@ a16! C++++>$ P++++>+++++$ L+++>+++++$ !E---? W+++>$ N- !o? !w--- O? !M? !V? !PS !PE--@ PGP+? r++ !t---?@ !X---? !R- b+ !tv b+ DI+ D+? G+++ e>+++++ !h++* r!-- y--
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