Re: [PATCH] mm, show_mem: drop pgdat_resize_lock in show_mem()

Wei Yang
2018-11-29T15:04:53Z

On Thu, Nov 29, 2018 at 09:17:03AM +0100, Michal Hocko wrote:
>On Thu 29-11-18 05:08:15, Wei Yang wrote:
>> Function show_mem() is used to print system memory status when user
>> requires or fail to allocate memory. Generally, this is a best effort
>> information and not willing to affect core mm subsystem.
>
>I would drop the part after and
>
>> The data protected by pgdat_resize_lock is mostly correct except there is:
>>
>> * page struct defer init
>> * memory hotplug
>
>This is more confusing than helpful. I would just drop it.
>
>The changelog doesn't explain what is done and why. The second one is
>much more important. I would say this
>
>"
>Function show_mem() is used to print system memory status when user
>requires or fail to allocate memory. Generally, this is a best effort
>information so any races with memory hotplug (or very theoretically an
>early initialization) should be toleratable and the worst that could
>happen is to print an imprecise node state.
>
>Drop the resize lock because this is the only place which might hold the

As I mentioned in https://patchwork.kernel.org/patch/10689759/, there is
one place used in __remove_zone(). I don't get your suggestion of this
place. And is __remove_zone() could be called in IRQ context?

>lock from the interrupt context and so all other callers might use a
>simple spinlock. Even though this doesn't solve any real issue it makes
>the code easier to follow and tiny more effective.
>"
>

--
Wei Yang
Help you, Help me