Re: [PATCH 1/3] mm, memcg: Don't put offlined memcg into local stock

[Waiman Long <longman@redhat.com>]

On 1/31/22 12:09, Waiman Long wrote:
> On 1/31/22 12:01, Roman Gushchin wrote:
>> On Sun, Jan 30, 2022 at 10:55:56PM -0500, Waiman Long wrote:
>>> On 10/1/21 19:51, Roman Gushchin wrote:
>>>> On Fri, Oct 01, 2021 at 03:09:36PM -0400, Waiman Long wrote:
>>>>> When freeing a page associated with an offlined memcg, refill_stock()
>>>>> will put it into local stock delaying its demise until another memcg
>>>>> comes in to take its place in the stock. To avoid that, we now check
>>>>> for offlined memcg and go directly in this case to the slowpath for
>>>>> the uncharge via the repurposed cancel_charge() function.
>>>> Hi Waiman!
>>>>
>>>> I'm afraid it can make a cleanup of a dying cgroup slower: for every
>>>> released page we'll potentially traverse the whole cgroup tree and
>>>> decrease atomic page counters.
>>>>
>>>> I'm not sure I understand the benefits we get from this change which
>>>> do justify the slowdown on the cleanup path.
>>>>
>>>> Thanks!
>>> I was notified of a lockdep splat that this patch may help to prevent.
>> Would you mind to test this patch:
>> https://www.spinics.net/lists/cgroups/msg31244.html ?
>>
>> It should address this dependency.
>
> Thanks for the pointer. I believe that your patch should be able to 
> address this circular locking dependency.
>
> Feel free to add my
>
> Reviewed-by: Waiman Long <longman@redhat.com>

BTW, have you posted it to lkml? If not, would you mind doing so?

Thanks,
Longman