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From: Pingfan Liu <kernelfans@gmail.com>
Date: Mon, 9 Sep 2019 15:35:53 +0800
Message-ID: <CAFgQCTs_+bOxLKeD8rfqjbkXOeEm7xbSVj0z7pby9M=Qj6Tedg@mail.gmail.com>
Subject: Re: [PATCH] powerpc/crashkernel: take mem option into account
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Cc: Hari Bathini <hbathini@linux.ibm.com>
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On Mon, Sep 9, 2019 at 12:05 PM Pingfan Liu <kernelfans@gmail.com> wrote:
>
> 'mem=" option is an easy way to put high pressure on memory during some
> test. Hence in stead of total mem, the effective usable memory size should
> be considered when reserving mem for crashkernel. Otherwise the boot up may
> experience oom issue.
>
> E.g passing
> crashkernel="2G-4G:384M,4G-16G:512M,16G-64G:1G,64G-128G:2G,128G-:4G", and
> mem=5G.
>
> Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
> Cc: Hari Bathini <hbathini@linux.ibm.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> To: linuxppc-dev@lists.ozlabs.org
> ---
>  arch/powerpc/kernel/machine_kexec.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
> index c4ed328..714b733 100644
> --- a/arch/powerpc/kernel/machine_kexec.c
> +++ b/arch/powerpc/kernel/machine_kexec.c
> @@ -114,11 +114,12 @@ void machine_kexec(struct kimage *image)
>
>  void __init reserve_crashkernel(void)
>  {
> -       unsigned long long crash_size, crash_base;
> +       unsigned long long crash_size, crash_base, total_mem_sz;
>         int ret;
>
> +       total_mem_sz = memory_limit ? memory_limit : memblock_phys_mem_size();
Here memory_limit is used to esstimation and may be changed.
So I think it is better to use memory_limit here than moving
memblock_enforce_memory_limit() before the call to
reserve_crashkernel()

Thanks,
Pingfan
>         /* use common parsing */
> -       ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
> +       ret = parse_crashkernel(boot_command_line, total_mem_sz,
>                         &crash_size, &crash_base);
>         if (ret == 0 && crash_size > 0) {
>                 crashk_res.start = crash_base;
> --
> 2.7.5
>