Re: [PATCH] net: limit a number of namespaces which can be cleaned up concurrently

From: ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman)
Date: Thu, 13 Oct 2016 22:06:28 -0500

Oh that is a surprise.  We can definitely skip genenerating uevents for
network namespaces that are exiting because by definition no one can see
those network namespaces.  If a socket existed that could see those
uevents it would hold a reference to the network namespace and as such
the network namespace could not exit.

That sounds like it is worth investigating a little more deeply.

I am surprised that allocation and freeing is so heavy we are spending
lots of time doing that.  On the other hand kobj_bcast_filter is very
dumb and very late so I expect something can be moved earlier and make
that code cheaper with the tiniest bit of work.

I definitely would rather see the uevents removed to kill ~%99 of the
namespace removal overhead rather than limiting.