Re: [PATCH 1/3] mm/memcg: Fix min/low usage in propagate_protected_usage()

Xunlei Pang
2018-12-05T08:59:32Z

Hi Roman,

On 2018/12/4 AM 2:00, Roman Gushchin wrote:
> On Mon, Dec 03, 2018 at 04:01:17PM +0800, Xunlei Pang wrote:
>> When usage exceeds min, min usage should be min other than 0.
>> Apply the same for low.
>>
>> Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com>
>> ---
>> mm/page_counter.c | 12 ++----------
>> 1 file changed, 2 insertions(+), 10 deletions(-)
>>
>> diff --git a/mm/page_counter.c b/mm/page_counter.c
>> index de31470655f6..75d53f15f040 100644
>> --- a/mm/page_counter.c
>> +++ b/mm/page_counter.c
>> @@ -23,11 +23,7 @@ static void propagate_protected_usage(struct page_counter *c,
>> return;
>>
>> if (c->min || atomic_long_read(&c->min_usage)) {
>> - if (usage <= c->min)
>> - protected = usage;
>> - else
>> - protected = 0;
>> -
>> + protected = min(usage, c->min);
>
> This change makes sense in the combination with the patch 3, but not as a
> standlone "fix". It's not a bug, it's a required thing unless you start scanning
> proportionally to memory.low/min excess.
>
> Please, reflect this in the commit message. Or, even better, merge it into
> the patch 3.

The more I looked the more I think it's a bug, but anyway I'm fine with
merging it into patch 3 :-)

>
> Also, please, make sure that cgroup kselftests are passing after your changes.

Sure, will do and send v2. Thanks for your inputs.