Re: [RFC PATCH 0/3] Memory Controller eBPF support

[hui . zhu]

2025年11月27日 00:01, "Michal Hocko" <mhocko@xxxxxxxx mailto:mhocko@xxxxxxxx?to=%22Michal%20Hocko%22%20%3Cmhocko%40suse.com%3E > 写到:


> 
> On Wed 26-11-25 03:05:32, hui.zhu@xxxxxxxxx wrote:
> 
> > 
> > 2025年11月25日 20:55, "Michal Hocko" <mhocko@xxxxxxxx mailto:mhocko@xxxxxxxx?to=%22Michal%20Hocko%22%20%3Cmhocko%40suse.com%3E > 写到:
> >  
> >  
> >  
> >  On Tue 25-11-25 12:39:11, hui.zhu@xxxxxxxxx wrote:
> >  
> >  > 
> >  > My goal is implement dynamic memory reclamation for memcgs without limits,
> >  > triggered by specific conditions.
> >  > 
> >  > For instance, with memcg A and memcg B both unlimited, when memcg A faces
> >  > high PSI pressure, ebpf control memcg B do some memory reclaim work when
> >  > it try charge.
> >  > 
> >  Understood. Please also think whether this is already possible with
> >  existing interfaces and if not what are roadblocks in that direction.
> >  
> >  I think it's possible to implement a userspace program using the existing
> >  PSI userspace interfaces and the control interfaces provided by memcg to
> >  accomplish this task.
> >  However, this approach has several limitations:
> >  the entire process depends on the continuous execution of the userspace
> >  program, response latency is higher, and we cannot perform fine-grained
> >  operations on target memcg.
> > 
> I will need to back these arguments by some actual numbers.

Agree – I’ll implement a PoC show it.

Best,
Hui

> 
> > 
> > Now that Roman has provided PSI eBPF functionality at
> >  https://lore.kernel.org/lkml/20251027231727.472628-1-roman.gushchin@xxxxxxxxx/
> >  Maybe we could add eBPF support to memcg as well, allowing us to implement
> >  the entire functionality directly in the kernel through eBPF.
> > 
> His usecase is very specific to OOM handling and we have agreed that
> this specific usecase is really tricky to achieve from userspace. I
> haven't see sound arguments for this usecase yet.
> -- 
> Michal Hocko
> SUSE Labs
>