Messages in this thread | | | Date | Mon, 11 Mar 2013 12:04:38 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] x86, kdump: Set crashkernel_low automatically |
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On 03/11/2013 12:02 PM, Vivek Goyal wrote: >> >> What is the purpose of reserving that kind of memory below 896 MB? If >> you have a 32-bit system, it will likely be useless since you are >> robbing the primary of most of lowmem, on a 64-bit system 896 MB is not >> a magic value in any way...? > > Actually I am not sure where did 896MB magic value had come from for > x86_64 so far. I assumed that it was some kexec-tools limitation so > first trying 896MB will preserve working with old kexec-tools. If it > was some kernel limitation, then I agree it should not be required anymore. > > I do remember that old pugatory had 2G limit. So may be we can first > try reserve with-in first 2G, then with-in first 4G and then above > 4G. (Assuming 896M was not kexec-tools limitation and had something > to do with kernel/initramfs). >
It is obvious where it *originated* from... it is the *default* (but not necessarily the actual!) HIGHMEM crossover point on x86-32.
Whether this limitation has crept into somewhere else is a good question.
-hpa
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