Re: [RFC]: userspace memory reaping

On Tue, Nov 03, 2020 at 01:40:41PM -0800, Suren Baghdasaryan wrote:

On Tue, Nov 3, 2020 at 1:32 PM Minchan Kim [off-list ref] wrote:

quoted

On Tue, Nov 03, 2020 at 10:35:50AM +0100, Michal Hocko wrote:

quoted

On Mon 02-11-20 12:29:24, Suren Baghdasaryan wrote:
[...]

quoted

To follow up on this. Should I post an RFC implementing SIGKILL_SYNC
which in addition to sending a kill signal would also reap the
victim's mm in the context of the caller? Maybe having some code will
get the discussion moving forward?

Yeah, having a code, even preliminary, might help here. This definitely
needs a good to go from process management people as that proper is land
full of surprises...

Just to remind a idea I suggested to reuse existing concept

    fd = pidfd_open(victim process)
    fdatasync(fd);
    close(fd);

Yep, I just posted a comment about that. I think though your above
sequence is missing a pidfd_send_signal(fd, SIGKILL) before the
fdatasync(fd)...
Not sure if fdatasync(pidfd) or fsync(pidfd) would be more appropriate
for this but will use one and we can discuss details in the RFC with
the code.

IMO, fdatasync would be better symantic since fsync invovles metadata
(i.e., task_struct, mm_struct and so on). I think what you need is
just pages attached to address_space, which sounds like data, not
metadata.