> On Feb 14, 2022, at 2:05 PM, Paul E. McKenney <paulmck@xxxxxxxxxx> wrote: > > Experimental. Not for inclusion. Yet, anyway. > > Freeing large numbers of namespaces in quick succession can result in > a bottleneck on the synchronize_rcu() invoked from kern_unmount(). > This patch applies the synchronize_rcu_expedited() hammer to allow > further testing and fault isolation. > > Hey, at least there was no need to change the comment! ;-) > I don’t think this will be fast enough. I think the problem is that commit e1eb26fa62d04ec0955432be1aa8722a97cb52e7 is putting all of the ipc namespace frees onto a list, and every free includes one call to synchronize_rcu() The end result is that we can create new namespaces much much faster than we can free them, and eventually we run out. I found this while debugging clone() returning ENOSPC because create_ipc_ns() was returning ENOSPC. -chris
