Re: [PATCH 0/2] mm: memory-failure: fix HWPoison flag race with non-atomic page flag ops

[David Hildenbrand (Arm)]

On 6/29/26 23:22, David Hildenbrand (Arm) wrote:
> [...]
> 
>>
>> And again, I'm really not sure fixing a theoretical race when memory
>> is failing is worth slowing the world by 0.1-1% for.
>>
> 
> Fully agreed. I was hoping RCU was cheaper (I mean, we were once told that RCU
> read side locking is essentially for free ... well in some configs :) )
> 
> The question if we could optimize it reasonably enough ...
> 
>>
>> From what I saw in my testing, if we allocate 4k pages
>> it's hidden by the overhead. With hp and thp it's measureably
>> worse than rcu on !preempt config.
> 
> ... for example, by doing the rcu read lock + unlock around the
> 
> 	for (i = 1; i < (1 << order); i++) {
> 
> loop on the alloc path. But I suspect it's not going to make that much of a
> difference.
> 
> I concluded, similar to Andi, that stop_machine() is too big of a hammer.
> 
> I wonder if something could be built out of preempt_disable() and sync SMP
> calls. hmm :(

Scrap that, shouldn't work I think ...

-- 
Cheers,

David