Re: crashkernel reservation failed - No suitable area found on a cortina/gemini SoC

[Bruce Mitchell]

On 4/7/2021 07:23, Corentin Labbe wrote:
> Le Wed, Apr 07, 2021 at 07:13:04AM -0700, Bruce Mitchell a écrit :
> > On 4/7/2021 05:54, Corentin Labbe wrote:
> > > Hello
> > >
> > > I try to do kexec on a cortina/gemini SoC.
> > > On a "normal" boot, kexec fail to find memory so I added crashkernel=8M to cmdline. (kernel size is ~6M).
> > > But now, kernel fail to reserve memory:
> > > Load Kern image from 0x30020000 to 0x800000 size 7340032
> > > Booting Linux on physical CPU 0x0
> > > Linux version 5.12.0-rc5-next-20210401+ (compile@Red) (armv7a-unknown-linux-gnueabihf-gcc (Gentoo 9.3.0-r2 p4) 9.3.0, GNU ld (Gentoo 2.34 p6) 2.34.0) #98 PREEMPT Wed Apr 7 14:14:08 CEST 2021
> > > CPU: FA526 [66015261] revision 1 (ARMv4), cr=0000397f
> > > CPU: VIVT data cache, VIVT instruction cache
> > > OF: fdt: Machine model: Edimax NS-2502
> > > Memory policy: Data cache writeback
> > > Zone ranges:
> > >     Normal   [mem 0x0000000000000000-0x0000000007ffffff]
> > >     HighMem  empty
> > > Movable zone start for each node
> > > Early memory node ranges
> > >     node   0: [mem 0x0000000000000000-0x0000000007ffffff]
> > > Initmem setup node 0 [mem 0x0000000000000000-0x0000000007ffffff]
> > > crashkernel reservation failed - No suitable area found.
> > > Built 1 zonelists, mobility grouping on.  Total pages: 32512
> > > Kernel command line: console=ttyS0,19200n8 ip=dhcp crashkernel=8M
> > > Dentry cache hash table entries: 16384 (order: 4, 65536 bytes, linear)
> > > Inode-cache hash table entries: 8192 (order: 3, 32768 bytes, linear)
> > > mem auto-init: stack:off, heap alloc:off, heap free:off
> > > Memory: 119476K/131072K available (5034K kernel code, 579K rwdata, 1372K rodata, 3020K init, 210K bss, 11596K reserved, 0K cma-reserved, 0K highmem)
> > > SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
> > >
> > > What can I do ?
> > >
> > > Thanks
> > > Regards
> > >
> > > _______________________________________________
> > > kexec mailing list
> > > kexec@xxxxxxxxxxxxxxxxxxx
> > > http://lists.infradead.org/mailman/listinfo/kexec
> >
> > Hello Corentin,
> >
> > I see much larger crashkernel=xxM being shown here
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/admin-guide/kdump/kdump.rst
> > and from many of my other searches.
> >
> > Here is an interesting article on kdump for ARM-32
> > https://kaiwantech.wordpress.com/2017/07/13/setting-up-kdump-and-crash-for-arm-32-an-ongoing-saga/
> >
> >
> > Here is the kernel command line reference
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/admin-guide/kernel-parameters.txt?h=v5.11#n732
> >
> > I feel your frustrations too.
>
> Hello
>
> Thanks but I have already read those documentation.
> I search to know why the kernel cannot find 8M of memory ouf of 128.
>
> Regards

How much more memory does the kernel and initrd above and beyond just 
their physical size?  (heaps, stacks, buffers, virtual filesystems)