Re: [PATCH v9 0/8] stg mail -e --version=v9 \

[David Hildenbrand]

On 11.09.19 15:51, Michal Hocko wrote:
> On Wed 11-09-19 15:20:02, Michal Hocko wrote:
> [...]
>>> 4. Continuously report, not the "one time report everything" approach.
>>
>> So you mean the allocator reporting this rather than an external code to
>> poll right? I do not know, how much this is nice to have than must have?
> 
> Another idea that I haven't really thought through so it might turned
> out to be completely bogus but let's try anyway. Your "report everything"
> just made me look and realize that free_pages_prepare already performs
> stuff that actually does something similar yet unrelated.
> 
> We do report to special page poisoning, zeroying or
> CONFIG_DEBUG_PAGEALLOC to unmap the address from the kernel address
> space. This sounds like something fitting your model no?
> 

AFAIKS, the poisoning/unmapping is done whenever a page is freed. I
don't quite see yet how that would help to remember if a page was
already reported. After reporting the page we would have to switch some
state (Nitesh: bitmap bit, Alexander: page flag) to identify that.

Of course, we could map the page and treat that as "the state" when we
reported it, but I am not sure that's such a good idea :)

As always, I might be very wrong ...

-- 

Thanks,

David / dhildenb