Re: [PATCH] mm/memory-failure: allow memory allocation from emergency reserves

[Miaohe Lin <linmiaohe@huawei.com>]

On 2024/7/2 15:19, Andrew Morton wrote:
> On Sat, 29 Jun 2024 10:09:46 +0800 Miaohe Lin <linmiaohe@huawei.com> wrote:
> 
>> On 2024/6/25 10:23, Rui Qi wrote:
>>> From: Rui Qi <qirui.001@bytedance.com>
>>>
>>> we hope that memory errors can be successfully handled quickly, using
>>> __GFP_MEMALLOC can help us improve the success rate of processing
>>
>> Comments of __GFP_MEMALLOC says:
>>
>>  * Users of this flag have to be extremely careful to not deplete the reserve
>>  * completely and implement a throttling mechanism which controls the
>>  * consumption of the reserve based on the amount of freed memory.
>>
>> It seems there's no such throttling mechanism in memory_failure.
>>
>>> under memory pressure, because to_kill struct is freed very quickly,
>>> so using __GFP_MEMALLOC will not exacerbate memory pressure for a long time,
>>> and  more memory will be freed after killed task exiting, which will also
>>
>> Tasks might not be killed even to_kill struct is allocated.
>>
>> ...
>>
>>> -	raw_hwp = kmalloc(sizeof(struct raw_hwp_page), GFP_ATOMIC);
>>> +	raw_hwp = kmalloc(sizeof(struct raw_hwp_page), GFP_ATOMIC | __GFP_MEMALLOC);
>>
>> In already hardware poisoned code path, raw_hwp can be allocated to store raw page info
>> without killing anything. So __GFP_MEMALLOC might not be suitable to use.
>> Or am I miss something?
> 
> Yes, I'm doubtful about this patch.  I think that rather than poking at a
> particular implementation, it would be helpful for us to see a complete
> description of the issues which were observed, please.  Let's see the
> bug report and we can discuss fixes later.

I agree with you, Andrew. Thanks. :)
.