linux-kernel - Re: [PATCH 2/2] MIPS: Select ARCH_KEEP_MEMBLOCK to enable sysfs memblock debug

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Date:   Thu, 3 Dec 2020 11:58:51 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>
Subject: Re: [PATCH 2/2] MIPS: Select ARCH_KEEP_MEMBLOCK to enable sysfs
 memblock debug



在 2020/12/3 上午11:19, Tiezhu Yang 写道:
> In the current code, CONFIG_ARCH_KEEP_MEMBLOCK is not set for MIPS arch,
> memblock_discard() will discard memory and reserved arrays if they were
> allocated, select ARCH_KEEP_MEMBLOCK to give a chance to track "memory"
> and "reserved" memblocks after early boot, with this patch, we can see
> the following two sysfs interfaces under DEBUG_FS.
>
> /sys/kernel/debug/memblock/memory
> /sys/kernel/debug/memblock/reserved

Is this really necessary?
memblock data is not really necessary after boot for non-debug purpose.

Given that MIPS is widely used in embedded systems which doesn't have much
memory, keeping unused data after boot is kinda unconvincing.

If you intend to debug that please do it locally.

Thanks.

- Jiaxun


>
> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
> ---
>   arch/mips/Kconfig | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 44a47ad..f65da197 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -9,6 +9,7 @@ config MIPS
>   	select ARCH_HAS_PTE_SPECIAL if !(32BIT && CPU_HAS_RIXI)
>   	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>   	select ARCH_HAS_UBSAN_SANITIZE_ALL
> +	select ARCH_KEEP_MEMBLOCK
>   	select ARCH_SUPPORTS_UPROBES
>   	select ARCH_USE_BUILTIN_BSWAP
>   	select ARCH_USE_CMPXCHG_LOCKREF if 64BIT