lkml.org 
[lkml]   [2022]   [Oct]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: RFC [PATCH v4 2/7] Enable balloon drivers to report inflated memory
From
>>>> Sounds to me that all you want is some notifier to be called from
>>>> adjust_managed_page_count(). What am I missing?
>>>
>>> Notifier will act as an accumulator to report size of change and it will make things easier for the drivers and users wrt locking.
>>> Notifier is similar to the memory hotplug notifier.
>>
>> Overall, I am not convinced that there is any value of separating the value
>> and the notifier. You can batch both or not batch both. In addition, as I
>> mentioned, having two values seems racy.
>
> I have identified two users so far above - may be more to come.
> One type needs the value to adjust. Also having the value is necessary
> to report it to users and oom. There are options with callbacks and so
> on but it will complicate things with no real gain. You are right about
> the atomicity but i guess if that's a problem for some user it could
> find a way to ensure it. i am yet to find such place.
>

I haven't followed the whole discussion, but I just wanted to raise that
having a generic mechanism to notify on such changes could be valuable.

For example, virtio-mem also uses adjust_managed_page_count() and might
sometimes not trigger memory hotplug notifiers when adding more memory
(essentially, when it fake-adds memory part of an already added Linux
memory block).

What might make sense is schedule some kind of deferred notification on
adjust_managed_page_count() changes. This way, we could notify without
caring about locking and would naturally batch notifications.

adjust_managed_page_count() users would not require changes.

--
Thanks,

David / dhildenb

\
 
 \ /
  Last update: 2022-10-11 11:23    [W:0.048 / U:2.508 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site