Re: [PATCH] Fix /proc/stat freezes (was [PATCH v15] "task_isolation" mode)

2016-09-28 Thread Frederic Weisbecker
On Wed, Aug 17, 2016 at 02:37:46PM -0500, Christoph Lameter wrote: > On Tue, 16 Aug 2016, Chris Metcalf wrote: > Subject: NOHZ: Correctly display increasing cputime when processor is busy > > The tick may be switched off when the processor gets busy with nohz full. > The user time fields in

Re: [PATCH v15 04/13] task_isolation: add initial support

2016-09-27 Thread Frederic Weisbecker
On Tue, Sep 27, 2016 at 04:39:26PM +0200, Peter Zijlstra wrote: > On Tue, Sep 27, 2016 at 04:22:20PM +0200, Frederic Weisbecker wrote: > > > The RCU context tracking doesn't take care of callbacks. It's only there > > to tell the RCU core whether the CPU runs code that may or m

Re: Ping: [PATCH v15 00/13] support "task_isolation" mode

2016-09-27 Thread Frederic Weisbecker
On Mon, Sep 12, 2016 at 08:20:16PM -0400, Francis Giraldeau wrote: > > The args are valid, but the system has an unstable clock, therefore the > operation is not supported. In the user point of view, maybe ENOTSUPP > would be more appropriate? But then, we need to check the reason and >

Re: Ping: [PATCH v15 00/13] support "task_isolation" mode

2016-09-27 Thread Frederic Weisbecker
can start using it. I had been thinking > >the obvious path was via Frederic Weisbecker to Ingo as a NOHZ kind of > >thing. But perhaps it touches enough other subsystems that that > >doesn't really make sense? Andrew, would it make sense to take it > >directly via your

Re: [PATCH v15 04/13] task_isolation: add initial support

2016-09-27 Thread Frederic Weisbecker
On Fri, Sep 02, 2016 at 10:28:00AM -0700, Andy Lutomirski wrote: > > Unless I'm missing something (which is reasonably likely), couldn't > the isolation code just force or require rcu_nocbs on the isolated > CPUs to avoid this problem entirely. rcu_nocb is already implied by nohz_full. Which

Re: [PATCH v14 04/14] task_isolation: add initial support

2016-09-03 Thread Frederic Weisbecker
On Tue, Aug 30, 2016 at 02:17:27PM -0400, Chris Metcalf wrote: > On 8/30/2016 1:36 PM, Chris Metcalf wrote: > >>>See the other thread with Peter Z for the longer discussion of this. > >>>At this point I'm leaning towards replacing the set_tsk_need_resched() with > >>> > >>>

Re: [PATCH v14 04/14] task_isolation: add initial support

2016-08-30 Thread Frederic Weisbecker
On Tue, Aug 30, 2016 at 11:41:36AM -0400, Chris Metcalf wrote: > On 8/29/2016 8:55 PM, Frederic Weisbecker wrote: > >On Mon, Aug 15, 2016 at 10:59:55AM -0400, Chris Metcalf wrote: > >>On 8/11/2016 2:50 PM, Christoph Lameter wrote: > >>>On Thu, 11 Aug 2016, Frederic We

Re: [PATCH v14 04/14] task_isolation: add initial support

2016-08-29 Thread Frederic Weisbecker
On Mon, Aug 15, 2016 at 10:59:55AM -0400, Chris Metcalf wrote: > On 8/11/2016 2:50 PM, Christoph Lameter wrote: > >On Thu, 11 Aug 2016, Frederic Weisbecker wrote: > > > >>Do we need to quiesce vmstat everytime before entering userspace? > >>I thought that vms

Re: clocksource_watchdog causing scheduling of timers every second (was [v13] support "task_isolation" mode)

2016-08-13 Thread Frederic Weisbecker
On Fri, Aug 12, 2016 at 09:19:19AM -0700, Paul E. McKenney wrote: > On Fri, Aug 12, 2016 at 04:26:13PM +0200, Frederic Weisbecker wrote: > > On Fri, Aug 12, 2016 at 09:23:13AM -0500, Christoph Lameter wrote: > > > On Thu, 11 Aug 2016, Paul E. McKenney wrote: > > > &g

Re: clocksource_watchdog causing scheduling of timers every second (was [v13] support "task_isolation" mode)

2016-08-12 Thread Frederic Weisbecker
On Fri, Aug 12, 2016 at 09:23:13AM -0500, Christoph Lameter wrote: > On Thu, 11 Aug 2016, Paul E. McKenney wrote: > > > Heh! The only really good idea is for clocks to be reliably in sync. > > > > But if they go out of sync, what do you want to do instead? > > For a NOHZ task? Write a message

Re: [PATCH v14 04/14] task_isolation: add initial support

2016-08-11 Thread Frederic Weisbecker
On Tue, Aug 09, 2016 at 04:29:46PM -0400, Chris Metcalf wrote: > +/* > + * Each time we try to prepare for return to userspace in a process > + * with task isolation enabled, we run this code to quiesce whatever > + * subsystems we can readily quiesce to avoid later interrupts. > + */ > +void

Re: [PATCH v9 04/13] task_isolation: add initial support

2016-06-29 Thread Frederic Weisbecker
On Fri, Jun 03, 2016 at 03:32:04PM -0400, Chris Metcalf wrote: > On 5/25/2016 9:07 PM, Frederic Weisbecker wrote: > >I don't remember how much I answered this email, but I need to finish that > >:-) > > Sorry for the slow response - it's been a busy week. I'm

Re: [PATCH v9 04/13] task_isolation: add initial support

2016-04-22 Thread Frederic Weisbecker
On Fri, Apr 08, 2016 at 12:34:48PM -0400, Chris Metcalf wrote: > On 4/8/2016 9:56 AM, Frederic Weisbecker wrote: > >On Wed, Mar 09, 2016 at 02:39:28PM -0500, Chris Metcalf wrote: > >> TL;DR: Let's make an explicit decision about whether task isolation > >> should b

Re: [PATCH v9 04/13] task_isolation: add initial support

2016-04-08 Thread Frederic Weisbecker
On Wed, Mar 09, 2016 at 02:39:28PM -0500, Chris Metcalf wrote: > Frederic, > > Thanks for the detailed feedback on the task isolation stuff. > > This reply kind of turned into an essay, so I've added a little "TL;DR" > sentence before each section. I think I'm going to cut my reply into several

Re: [PATCH v9 04/13] task_isolation: add initial support

2016-01-30 Thread Frederic Weisbecker
On Fri, Jan 29, 2016 at 01:18:05PM -0500, Chris Metcalf wrote: > On 01/27/2016 07:28 PM, Frederic Weisbecker wrote: > >On Tue, Jan 19, 2016 at 03:45:04PM -0500, Chris Metcalf wrote: > >>You asked what happens if nohz_full= is given as well, which is a very > >>good q