Re: [PATCH mm-new v3] mm/memcontrol: Add memory.stat_refresh for on-demand stats flushing

[Waiman Long <llong@redhat.com>]

On 11/11/25 2:47 PM, Michal Hocko wrote:
> On Tue 11-11-25 14:10:28, Waiman Long wrote:
> [...]
>>> +static void memcg_flush_stats(struct mem_cgroup *memcg, bool force)
>>> +{
>>> +	if (mem_cgroup_disabled())
>>> +		return;
>>> +
>>> +	memcg = memcg ?: root_mem_cgroup;
>>> +	__mem_cgroup_flush_stats(memcg, force);
>>> +}
>> Shouldn't we impose a limit in term of how frequently this
>> memcg_flush_stats() function can be called like at most a few times per
> This effectivelly invalidates the primary purpose of the interface to
> provide a method to get as-fresh-as-possible value AFAICS.
>
>> second to prevent abuse from user space as stat flushing is expensive? We
>> should prevent some kind of user space DoS attack by using this new API if
>> we decide to implement it.
> What exactly would be an attack vector?

just repeatedly write a string to the new cgroup file. It will then call 
css_rstat_flush() repeatedly. It is not a real DoS attack, but it can 
still consume a lot of cpu time and slow down other tasks.

Cheers,
Longman