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

[Waiman Long]

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