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

[Bruce Mitchell <bruce.mitchell@linux.vnet.ibm.com>]

On 4/7/2021 07:48, Corentin Labbe wrote:
> Le Wed, Apr 07, 2021 at 07:28:26AM -0700, Bruce Mitchell a écrit :
>> 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@lists.infradead.org
>>>>> 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)
> 
> The kernel size include a rootfs.cpio.lzma of 3MB and dtb is appended.
> The total kernel size is 7MB.
> The uncompressed size of the kernel is 13M (size of vmlinux)
> The uncompressed size of rootfs is 11M.
> 
> cat /proc/meminfo
> MemTotal:         122496 kB
> MemFree:          103700 kB
> MemAvailable:     101936 kB
> Buffers:               0 kB
> Cached:            10904 kB
> SwapCached:            0 kB
> Active:             4304 kB
> Inactive:           8012 kB
> Active(anon):       4304 kB
> Inactive(anon):     8012 kB
> Active(file):          0 kB
> Inactive(file):        0 kB
> Unevictable:           0 kB
> Mlocked:               0 kB
> HighTotal:             0 kB
> HighFree:              0 kB
> LowTotal:         122496 kB
> LowFree:          103700 kB
> SwapTotal:             0 kB
> SwapFree:              0 kB
> Dirty:                 0 kB
> Writeback:             0 kB
> AnonPages:          1428 kB
> Mapped:             3552 kB
> Shmem:             10904 kB
> KReclaimable:        608 kB
> Slab:               2960 kB
> SReclaimable:        608 kB
> SUnreclaim:         2352 kB
> KernelStack:         312 kB
> PageTables:          136 kB
> NFS_Unstable:          0 kB
> Bounce:                0 kB
> WritebackTmp:          0 kB
> CommitLimit:       61248 kB
> Committed_AS:      14336 kB
> VmallocTotal:     901120 kB
> VmallocUsed:          64 kB
> VmallocChunk:          0 kB
> Percpu:               32 kB
> CmaTotal:              0 kB
> CmaFree:               0 kB
> 

I believe you need space for all of that,
the smallest that would work for me was 20MB.