Jarod Wilson wrote:
carlopmart wrote:Jarod Wilson wrote:Removing the crashkernel parameter will disable kdump from being able to capture a vmcore in the event of a system crash, but yes, you can remove it without breaking anything else. So that explains where 128M of your memory went, and I can probably explain the rest: the xen hypervisor reserves some memory for itself that it doesn't expose even to the dom0 kernel.Thanks Jarod for your response. But, what are the minimum memory I need to reserve for crashkernel ??? will be 16 MB ok?? I don't want to disable this if I need it to debug some crash ...128MB is the safe route for the default kdump setup. Basically, you have to boot an entire kernel into userspace to capture a vmcore w/the default kdump setup. If you adjust settings in /etc/kdump.conf, dumping either to a partition (which can be your root partition) or a network target (nfs or ssh), kdump will dump the vmcore from within the kdump initrd, rather than going all the way to userspace, in which case, you should be able to get away with 64MB, or *maybe* less. I've not really tried much below 64MB, though I know of success cases w/48MB. I highly doubt it can be done in only 16MB though. How little you can make work is unfortunately still a trial and error thing, and probably always will be. The minimum memory requirements vary from machine to machine, depending on the number of pci cards in the system, motherboard resources, what dump method (local disk, nfs, ssh) you're using, etc., etc., so there's really no sane way to calculate a guaranteed functional minimum memory for kdump, which is why we default to 128M -- its enough that kdump Just Works for the vast majority of systems.
Many thanks Jarod.
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CL Martinez
carlopmart {at} gmail {d0t} com
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