Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1272193

Re: [PATCH 3/4] sched: introduce synchronized idle injection

Show all headers | View raw

On Wed, Nov 18, 2015 at 01:49:46PM +0100, Peter Zijlstra wrote:
> On Wed, Nov 18, 2015 at 12:27:04PM +0000, Morten Rasmussen wrote:
> > On Wed, Nov 18, 2015 at 11:35:41AM +0100, Peter Zijlstra wrote:
> > > On Wed, Nov 18, 2015 at 09:36:22AM +0100, Ingo Molnar wrote:
> > > > What will such throttling do to latencies, as observed by user-space tasks? What's 
> > > > the typical expected frequency of the throttling frequency that you are targeting?
> > > 
> > > The default has 5ms (iirc) of forced idle, so depending on what you do,
> > > noticeable to outright painful.
> > 
> > IIUC, it is 5 ticks, not ms.
> 
> The code uses hrtimers (badly), this means there _should_ not be a tick
> dependency.

Then I'm confused :-/

I see the hrtimers, but the actual idle duration appears to be in ticks
rather than ms and then converted later.

+/* Duration of idle time in ticks of each injection period */                                                                               
+unsigned int sysctl_sched_cfs_idle_inject_duration = 5UL;

...and futher down we have:

+       duration_msec = jiffies_to_msecs(sysctl_sched_cfs_idle_inject_duration);

I will go back and look harder.

> 
> > Which raises the question, doesn't that mean that we get disturbed four
> > times on each cpu during the forced idle period? So idle injection only
> > makes sense if the platform has package states with a target residency
> > less than a jiffy. Or, do we enter NOHZ idle? I haven't looked closely
> > enough to figure out yet.
> 
> The idea is to hit NOHZ.

Nice!
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Re: [PATCH 3/4] sched: introduce synchronized idle injection Ingo Molnar <mingo@kernel.org> - 2015-11-18 09:40 +0100
  Re: [PATCH 3/4] sched: introduce synchronized idle injection Peter Zijlstra <peterz@infradead.org> - 2015-11-18 11:40 +0100
    Re: [PATCH 3/4] sched: introduce synchronized idle injection Morten Rasmussen <morten.rasmussen@arm.com> - 2015-11-18 13:30 +0100
      Re: [PATCH 3/4] sched: introduce synchronized idle injection Peter Zijlstra <peterz@infradead.org> - 2015-11-18 14:00 +0100
        Re: [PATCH 3/4] sched: introduce synchronized idle injection Morten Rasmussen <morten.rasmussen@arm.com> - 2015-11-18 15:10 +0100
          Re: [PATCH 3/4] sched: introduce synchronized idle injection Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-18 16:00 +0100
            Re: [PATCH 3/4] sched: introduce synchronized idle injection Morten Rasmussen <morten.rasmussen@arm.com> - 2015-11-18 16:10 +0100
              Re: [PATCH 3/4] sched: introduce synchronized idle injection Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-18 16:20 +0100
                Re: [PATCH 3/4] sched: introduce synchronized idle injection Thomas Gleixner <tglx@linutronix.de> - 2015-11-18 16:30 +0100
                Re: [PATCH 3/4] sched: introduce synchronized idle injection Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-18 20:00 +0100
                Re: [PATCH 3/4] sched: introduce synchronized idle injection Morten Rasmussen <morten.rasmussen@arm.com> - 2015-11-18 17:10 +0100
    Re: [PATCH 3/4] sched: introduce synchronized idle injection Ingo Molnar <mingo@kernel.org> - 2015-11-27 10:20 +0100
  Re: [PATCH 3/4] sched: introduce synchronized idle injection Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-18 15:20 +0100
    Re: [PATCH 3/4] sched: introduce synchronized idle injection Ingo Molnar <mingo@kernel.org> - 2015-11-27 10:20 +0100
  Re: [PATCH 3/4] sched: introduce synchronized idle injection Arjan van de Ven <arjan@linux.intel.com> - 2015-11-18 15:30 +0100

csiph-web