Re: [PATCH RFC v2 tip/core/rcu] Maintain special bits at bottom of ->dynticks counter

2017-02-13 Thread Paul E. McKenney
On Mon, Feb 13, 2017 at 11:08:55AM -0800, Andy Lutomirski wrote: > On Mon, Feb 13, 2017 at 9:57 AM, Peter Zijlstra wrote: > > On Mon, Feb 13, 2017 at 09:01:04AM -0800, Paul E. McKenney wrote: > >> > I think I've asked this before, but why does this live in the guts of > >> > RCU? > >> > > >> > Sho

Re: [PATCH RFC v2 tip/core/rcu] Maintain special bits at bottom of ->dynticks counter

2017-02-13 Thread Andy Lutomirski
On Mon, Feb 13, 2017 at 9:57 AM, Peter Zijlstra wrote: > On Mon, Feb 13, 2017 at 09:01:04AM -0800, Paul E. McKenney wrote: >> > I think I've asked this before, but why does this live in the guts of >> > RCU? >> > >> > Should we lift this state tracking stuff out and make RCU and >> > NOHZ(_FULL) u

Re: [PATCH RFC v2 tip/core/rcu] Maintain special bits at bottom of ->dynticks counter

2017-02-13 Thread Paul E. McKenney
On Mon, Feb 13, 2017 at 06:57:50PM +0100, Peter Zijlstra wrote: > On Mon, Feb 13, 2017 at 09:01:04AM -0800, Paul E. McKenney wrote: > > > I think I've asked this before, but why does this live in the guts of > > > RCU? > > > > > > Should we lift this state tracking stuff out and make RCU and > > >

Re: [PATCH RFC v2 tip/core/rcu] Maintain special bits at bottom of ->dynticks counter

2017-02-13 Thread Peter Zijlstra
On Mon, Feb 13, 2017 at 09:01:04AM -0800, Paul E. McKenney wrote: > > I think I've asked this before, but why does this live in the guts of > > RCU? > > > > Should we lift this state tracking stuff out and make RCU and > > NOHZ(_FULL) users of it, or doesn't that make sense (reason)? > > The dynt

Re: [PATCH RFC v2 tip/core/rcu] Maintain special bits at bottom of ->dynticks counter

2017-02-13 Thread Paul E. McKenney
On Mon, Feb 13, 2017 at 01:21:15PM +0100, Peter Zijlstra wrote: > On Thu, Feb 09, 2017 at 03:51:03PM -0800, Paul E. McKenney wrote: > > Currently, IPIs are used to force other CPUs to invalidate their TLBs > > in response to a kernel virtual-memory mapping change. This works, but > > d

Re: [PATCH RFC v2 tip/core/rcu] Maintain special bits at bottom of ->dynticks counter

2017-02-13 Thread Peter Zijlstra
On Thu, Feb 09, 2017 at 03:51:03PM -0800, Paul E. McKenney wrote: > Currently, IPIs are used to force other CPUs to invalidate their TLBs > in response to a kernel virtual-memory mapping change. This works, but > degrades both battery lifetime (for idle CPUs) and real-time response >

[PATCH RFC v2 tip/core/rcu] Maintain special bits at bottom of ->dynticks counter

2017-02-09 Thread Paul E. McKenney
Currently, IPIs are used to force other CPUs to invalidate their TLBs in response to a kernel virtual-memory mapping change. This works, but degrades both battery lifetime (for idle CPUs) and real-time response (for nohz_full CPUs), and in addition results in unnecessary IPIs due t