Re: [PATCH] VFS: use synchronize_rcu_expedited() in namespace_unlock()

2017-11-28 Thread NeilBrown
On Mon, Nov 27 2017, Paul E. McKenney wrote: > On Mon, Nov 27, 2017 at 12:27:04PM +0100, Florian Weimer wrote: >> On 10/26/2017 02:27 PM, Paul E. McKenney wrote: >> >But just for completeness, one way to make this work across the board >> >might be to instead use call_rcu(), with the callback func

Re: [PATCH] VFS: use synchronize_rcu_expedited() in namespace_unlock()

2017-11-27 Thread Paul E. McKenney
On Mon, Nov 27, 2017 at 12:27:04PM +0100, Florian Weimer wrote: > On 10/26/2017 02:27 PM, Paul E. McKenney wrote: > >But just for completeness, one way to make this work across the board > >might be to instead use call_rcu(), with the callback function kicking > >off a workqueue handler to do the r

Re: [PATCH] VFS: use synchronize_rcu_expedited() in namespace_unlock()

2017-11-27 Thread Florian Weimer
On 10/26/2017 02:27 PM, Paul E. McKenney wrote: But just for completeness, one way to make this work across the board might be to instead use call_rcu(), with the callback function kicking off a workqueue handler to do the rest of the unmount. Of course, in saying that, I am ignoring any mutexes

Re: [PATCH] VFS: use synchronize_rcu_expedited() in namespace_unlock()

2017-10-26 Thread Paul E. McKenney
On Fri, Oct 27, 2017 at 11:45:08AM +1100, NeilBrown wrote: > On Thu, Oct 26 2017, Paul E. McKenney wrote: > > > On Thu, Oct 26, 2017 at 01:26:37PM +1100, NeilBrown wrote: > >> > >> The synchronize_rcu() in namespace_unlock() is called every time > >> a filesystem is unmounted. If a great many fi

Re: [PATCH] VFS: use synchronize_rcu_expedited() in namespace_unlock()

2017-10-26 Thread NeilBrown
On Thu, Oct 26 2017, Paul E. McKenney wrote: > On Thu, Oct 26, 2017 at 01:26:37PM +1100, NeilBrown wrote: >> >> The synchronize_rcu() in namespace_unlock() is called every time >> a filesystem is unmounted. If a great many filesystems are mounted, >> this can cause a noticable slow-down in, for

Re: [PATCH] VFS: use synchronize_rcu_expedited() in namespace_unlock()

2017-10-26 Thread Paul E. McKenney
On Thu, Oct 26, 2017 at 05:27:43AM -0700, Paul E. McKenney wrote: > On Thu, Oct 26, 2017 at 01:26:37PM +1100, NeilBrown wrote: > > > > The synchronize_rcu() in namespace_unlock() is called every time > > a filesystem is unmounted. If a great many filesystems are mounted, > > this can cause a noti

Re: [PATCH] VFS: use synchronize_rcu_expedited() in namespace_unlock()

2017-10-26 Thread Paul E. McKenney
On Thu, Oct 26, 2017 at 01:26:37PM +1100, NeilBrown wrote: > > The synchronize_rcu() in namespace_unlock() is called every time > a filesystem is unmounted. If a great many filesystems are mounted, > this can cause a noticable slow-down in, for example, system shutdown. > > The sequence: > mkd

[PATCH] VFS: use synchronize_rcu_expedited() in namespace_unlock()

2017-10-25 Thread NeilBrown
The synchronize_rcu() in namespace_unlock() is called every time a filesystem is unmounted. If a great many filesystems are mounted, this can cause a noticable slow-down in, for example, system shutdown. The sequence: mkdir -p /tmp/Mtest/{0..5000} time for i in /tmp/Mtest/*; do mount -t tmpf