linux-kernel - Re: [RFC PATCH] mm: memory-failure: add soft-offline stat in mf

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Message-ID: <098640ac-f1c1-95b6-e367-a2673c3ceaae@huawei.com>
Date: Fri, 29 Nov 2024 15:07:54 +0800
From: Miaohe Lin <linmiaohe@...wei.com>
To: "Tomohiro Misono (Fujitsu)" <misono.tomohiro@...itsu.com>, 'Jiaqi Yan'
	<jiaqiyan@...gle.com>
CC: "linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>,
	Naoya Horiguchi <nao.horiguchi@...il.com>
Subject: Re: [RFC PATCH] mm: memory-failure: add soft-offline stat in mf_stats

On 2024/11/28 13:46, Tomohiro Misono (Fujitsu) wrote:
>>>> On 2024/11/21 12:55, Tomohiro Misono wrote:
>>>>> commit 44b8f8bf2438 ("mm: memory-failure: add memory failure stats
>>>>
>>>> Sorry for late, I've been swamped recently.
>>>
>>> Hi,
>>> Thanks for your comments.
>>>
>>>>
>>>>> to sysfs") introduces per NUMA memory error stats which show
>>>>> breakdown of HardwareCorrupted of /proc/meminfo in
>>>>> /sys/devices/system/node/nodeX/memory_failure.
>>>>
>>>> Thanks for your patch.
>>>>
>>>>>
>>>>> However, HardwareCorrupted also counts soft-offline pages. So, add
>>>>> soft-offline stats in mf_stats too to represent more accurate status.
>>>>
>>>> Adding soft-offline stats makes sense to me.
>>>
>>> Thanks for confirming.
>>
>> Agreed with Miaohe.
>>
>>>
>>>>
>>>>>
>>>>> This updates total count as:
>>>>>   total = recovered + ignored + failed + delayed + soft_offline>
>>>>> Test example:
>>>>> 1) # grep HardwareCorrupted /proc/meminfo
>>>>>      HardwareCorrupted:     0 kB
>>>>> 2) soft-offline 1 page by madvise(MADV_SOFT_OFFLINE)
>>>>> 3) # grep HardwareCorrupted /proc/meminfo
>>>>>      HardwareCorrupted:     4 kB
>>>>>    # grep -r "" /sys/devices/system/node/node0/memory_failure
>>>>>    /sys/devices/system/node/node0/memory_failure/total:1
>>>>>    /sys/devices/system/node/node0/memory_failure/soft_offline:1
>>>>>    /sys/devices/system/node/node0/memory_failure/recovered:0
>>>>>    /sys/devices/system/node/node0/memory_failure/ignored:0
>>>>>    /sys/devices/system/node/node0/memory_failure/failed:0
>>>>>    /sys/devices/system/node/node0/memory_failure/delayed:0
>>>>>
>>>>> Signed-off-by: Tomohiro Misono <misono.tomohiro@...itsu.com>
>>>>> ---
>>>>> Hello
>>>>>
>>>>> This is RFC because I'm not sure adding SOFT_OFFLINE in enum
>>>>> mf_result is a right approach. Also, maybe is it better to move
>>>>> update_per_node_mf_stats() into num_poisoned_pages_inc()?
>>>>>
>>>>> I omitted some cleanups and sysfs doc update in this version to
>>>>> highlight changes. I'd appreciate any suggestions.
>>>>>
>>>>> Regards,
>>>>> Tomohiro Misono
>>>>>
>>>>>  include/linux/mm.h     | 2 ++
>>>>>  include/linux/mmzone.h | 4 +++-
>>>>>  mm/memory-failure.c    | 9 +++++++++
>>>>>  3 files changed, 14 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>>>>> index 5d6cd523c7c0..7f93f6883760 100644
>>>>> --- a/include/linux/mm.h
>>>>> +++ b/include/linux/mm.h
>>>>> @@ -3991,6 +3991,8 @@ enum mf_result {
>>>>>     MF_FAILED,      /* Error: handling failed */
>>>>>     MF_DELAYED,     /* Will be handled later */
>>>>>     MF_RECOVERED,   /* Successfully recovered */
>>>>> +
>>>>> +   MF_RES_SOFT_OFFLINE, /* Soft-offline */
>>>>
>>>> It might not be a good idea to add MF_RES_SOFT_OFFLINE here. 'mf_result' is used to record
>>>> the result of memory failure handler. So it might be inappropriate to add MF_RES_SOFT_OFFLINE here.
>>>
>>> Understood. As I don't see other suitable place to put ENUM value, how about changing like below?
>>> Or, do you prefer adding another ENUM type instead of this?
>>
>> I think SOFT_OFFLINE-ed is one of the results of successfully
>> recovered, and the other one is HARD_OFFLINE-ed. So how about make a
>> separate sub-ENUM for MF_RECOVERED? Something like:
> 
> Thanks for the suggestion.
> 
>>
>> enum mf_recovered_result {
>>   MF_RECOVERED_SOFT_OFFLINE,
>>   MF_RECOVERED_HARD_OFFLINE,
>> };
> 
> Ok.
> 
>>
>> And
>> 1. total = recovered + ignored + failed + delayed
>> 2. recovered = soft_offline + hard_offline
> 
> Do you mean mf_stats now have 7 entries in sysfs?
> (total, ignored, failed, delayed, recovered, hard_offline, soft_offline, then recovered = hard_offline + soft_offline)
> Or 6 entries ? (in that case, hard_offline = recovered - soft_offline)
> It might be simpler to understand for user if total is just the sum of other entries like this RFC,
> but I'd like to know other opinions.

Will it be better to have below items?
"
total
ignored
failed
dalayed
hard_offline
soft_offline
"

though this will break the previous interface.
Any thoughts?

Thanks.
.