Re: [PATCH] procfs/dmabuf: Add /proc//task//dmabuf_fds

Michal Hocko
2021-01-27T11:06:43Z

On Wed 27-01-21 11:53:55, Christian König wrote:
[...]
> In general processes are currently not held accountable for memory they
> reference through their file descriptors. DMA-buf is just one special case.

True

> In other words you can currently do something like this
>
> fd = memfd_create("test", 0);
> while (1)
>     write(fd, buf, 1024);
>
> and the OOM killer will terminate random processes, but never the one
> holding the memfd reference.

memfd is just shmem under cover, no? And that means that the memory gets
accounted to MM_SHMEMPAGES. But you are right that this in its own
doesn't help much if the fd is shared and the memory stays behind a
killed victim.

But I do agree with you that there are resources which are bound to a
process life time but the oom killer has no idea about those as they are
not accounted on a per process level and/or oom_badness doesn't take
them into consideration.
--
Michal Hocko
SUSE Labs