Re: [PATCH -next 1/5] mm/mglru: use mem_cgroup_iter for global reclaim

Chen Ridong
2025-12-23T00:45:42Z

On 2025/12/23 5:18, Shakeel Butt wrote:
> On Mon, Dec 22, 2025 at 03:27:26PM +0800, Chen Ridong wrote:
>>
> [...]
>>
>>>> - if (should_abort_scan(lruvec, sc))
>>>> + if (should_abort_scan(lruvec, sc)) {
>>>> + if (cookie)
>>>> + mem_cgroup_iter_break(target, memcg);
>>>> break;
>>>
>>> This seems buggy as we may break the loop without calling
>>> mem_cgroup_iter_break(). I think for kswapd the cookie will be NULL and
>>> if should_abort_scan() returns true, we will break the loop without
>>> calling mem_cgroup_iter_break() and will leak a reference to memcg.
>>>
>>
>> Thank you for catching that—my mistake.
>>
>> This also brings up another point: In kswapd, the traditional LRU iterates through all memcgs, but
>> stops for the generational LRU (GENLRU) when should_abort_scan is met (i.e., enough pages are
>> reclaimed or the watermark is satisfied). Shouldn't both behave consistently?
>>
>> Perhaps we should add should_abort_scan(lruvec, sc) in shrink_node_memcgs for the traditional LRU as
>> well?
>
> We definitely should discuss about should_abort_scan() for traditional
> reclaim but to keep things simple, let's do that after this series. For
> now, follow Johannes' suggestion of lru_gen_should_abort_scan().
>

Okey, understood.

--
Best regards,
Ridong