Re: [RFC 2/2] signal: extend pidfd_send_signal() to allow expedited process killing

[Johannes Weiner]

On Thu, Apr 11, 2019 at 08:33:13AM -0700, Matthew Wilcox wrote:
> On Wed, Apr 10, 2019 at 06:43:53PM -0700, Suren Baghdasaryan wrote:
> > Add new SS_EXPEDITE flag to be used when sending SIGKILL via
> > pidfd_send_signal() syscall to allow expedited memory reclaim of the
> > victim process. The usage of this flag is currently limited to SIGKILL
> > signal and only to privileged users.
> 
> What is the downside of doing expedited memory reclaim?  ie why not do it
> every time a process is going to die?

I agree with this. The oom reaper mostly does work the exiting task
would have to do anyway, so this shouldn't be measurably more
expensive to do it per default. I wouldn't want to add a new interface
unless we really do need that type of control.