Re: [PATCH v2 13/23] mm: introduce bpf_out_of_memory() BPF kfunc

Michal Hocko
2025-11-10T09:46:18Z

On Mon 27-10-25 16:21:56, Roman Gushchin wrote:
> Introduce bpf_out_of_memory() bpf kfunc, which allows to declare
> an out of memory events and trigger the corresponding kernel OOM
> handling mechanism.
>
> It takes a trusted memcg pointer (or NULL for system-wide OOMs)
> as an argument, as well as the page order.
>
> If the BPF_OOM_FLAGS_WAIT_ON_OOM_LOCK flag is not set, only one OOM
> can be declared and handled in the system at once, so if the function
> is called in parallel to another OOM handling, it bails out with -EBUSY.
> This mode is suited for global OOM's: any concurrent OOMs will likely
> do the job and release some memory. In a blocking mode (which is
> suited for memcg OOMs) the execution will wait on the oom_lock mutex.

Rather than relying on BPF_OOM_FLAGS_WAIT_ON_OOM_LOCK would it make
sense to take the oom_lock based on the oc->memcg so that this is
completely transparent to specific oom bpf handlers?
--
Michal Hocko
SUSE Labs