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Subject: Re: crashkernel reservation failed - No suitable area found on a
 cortina/gemini SoC
To:     Corentin Labbe <clabbe.montjoie@gmail.com>
Cc:     ebiederm@xmission.com, kexec@lists.infradead.org,
        linux-kernel@vger.kernel.org
References: <YG2rfzRvHIZKXkf/@Red>
 <34ff1fcc-e9ee-02c2-b2a8-d98a24ce94c3@linux.vnet.ibm.com>
 <YG3AZ4K2auqEz9BK@Red>
From:   Bruce Mitchell <bruce.mitchell@linux.vnet.ibm.com>
Message-ID: <7a75028b-4495-cd51-6a32-59fcf6e0f166@linux.vnet.ibm.com>
Date:   Wed, 7 Apr 2021 07:28:26 -0700
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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)