[PATCH v26 0/7] arm64: add kdump support
mark.rutland at arm.com
Tue Oct 4 03:18:33 PDT 2016
On Mon, Oct 03, 2016 at 06:11:40PM +0530, Manish Jaggi wrote:
> On 10/03/2016 04:34 PM, AKASHI Takahiro wrote:
> > On Mon, Oct 03, 2016 at 01:24:34PM +0530, Manish Jaggi wrote:
> >> Observations:
> >> 1.1. Dump capture kernel shows different memory map.
> >> ---------------------------------------------------
> >> In dump capture kernel /proc/meminfo and /proc/iomem differ
> >> root at arm64:/home/ubuntu/CODE/crash#
> >> MemTotal: 65882432 kB
> >> MemFree: 65507136 kB
> >> MemAvailable: 60373632 kB
> >> Buffers: 29248 kB
> >> Cached: 46720 kB
> >> SwapCached: 0 kB
> >> Active: 63872 kB
> >> Inactive: 19776 kB
> >> Active(anon): 8256 kB
> >> Inactive(anon): 7616 kB
> >> First kernel is booted with mem=2G crashkernel=1G command line option.
> >> While the system has 64G memory.
> >> root at arm64:/home/ubuntu/CODE/crash# cat /proc/iomem
> >> 41400000-fffeffff : System RAM
> >> 41480000-420cffff : Kernel code
> >> 42490000-4278ffff : Kernel data
> >> ffff0000-ffffffff : reserved
> >> 100000000-ffaa7ffff : System RAM
> >> ffaa80000-ffaabffff : reserved
> >> ffaac0000-fffa6ffff : System RAM
> >> fffa70000-fffacffff : reserved
> >> fffad0000-fffffffff : System RAM
> > Are you saying that "mem=..." doesn't have any effect?
> What I am saying it that If the first kernel is booted using mem= option and crashkernel= option
> the memory for second kernel has to be withing the crashkernel size.
Please don't try to use mem= to limit the kernel to a specific range of
memory. It's really only there as a tool to test handling of low-memory
While it guarantees that at most, the amount requested will be used
(modulo a number of edge cases with reserved memory ranges), it does not
guarantee *which* memory will be used. It is *very* fragile.
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