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

Groups > linux.kernel > #1270711

Re: [PATCH 2/4] timer: relax tick stop in idle entry

From "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Newsgroups linux.kernel
Subject Re: [PATCH 2/4] timer: relax tick stop in idle entry
Date 2015-11-17 01:10 +0100
Message-ID <qvC0r-5SY-27@gated-at.bofh.it> (permalink)
References (5 earlier) <qvABj-4Q6-5@gated-at.bofh.it> <qvBe1-5kg-5@gated-at.bofh.it> <qvBnH-5nT-9@gated-at.bofh.it> <qvBxo-5rG-25@gated-at.bofh.it> <qvBH3-5vs-13@gated-at.bofh.it>
Organization linux.* mail to news gateway

Show all headers | View raw

On Mon, Nov 16, 2015 at 03:40:46PM -0800, Jacob Pan wrote:
> On Mon, 16 Nov 2015 15:32:38 -0800
> Arjan van de Ven <arjan@linux.intel.com> wrote:
> 
> > On 11/16/2015 3:28 PM, Paul E. McKenney wrote:
> > 
> > > Is this mostly an special-purpose embedded thing, or do you expect
> > > distros to be enabling this?  If the former, I suggest
> > > , but if distros are doing this for
> > > general-purpose workloads, I instead suggest CONFIG_RCU_FAST_NO_HZ.
> > 
> > thermal overload happens a lot on small devices, but sadly also in
> > big datacenters where it is not uncommon to underprovision cooling
> > capacity by a bit (it's one of those "99% of the time you only need
> > THIS much, the 1% you need 30% more" and that more is expensive or
> > even impractical)

Then CONFIG_RCU_FAST_NO_HZ it is.

> CONFIG_RCU_FAST_NO_HZ is more inline with idle injection in that both
> are targeted energy efficiency.
> Checking ubuntu and fedora, seems both have CONFIG_RCU_NOCB_CPU_ALL=y.

Ah, that is right -- they both do CONFIG_NO_HZ_FULL=y, which does imply
CONFIG_RCU_NOCB_CPU_ALL=y.  But SUSE does not, last I knew.

But it should be easy to set up Kconfig for this.  Make your new Kconfig
option select CONFIG_RCU_FAST_NO_HZ unless CONFIG_RCU_NOCB_CPU_ALL is
already set.  Alternatively, CONFIG_RCU_FAST_NO_HZ could be set up
something like the following:

	depends on (NO_HZ_COMMON && SMP && RCU_EXPERT) || CONFIG_THERM_THROT
	default CONFIG_THERM_THROT

But the "select RCU_FAST_NO_HZ if !RCU_NOCB_CPU_ALL" is probably cleaner.

Anyway, again, the details can be settled later.

							Thanx, Paul

--
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 2/4] timer: relax tick stop in idle entry Thomas Gleixner <tglx@linutronix.de> - 2015-11-16 16:10 +0100
  Re: [PATCH 2/4] timer: relax tick stop in idle entry Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-16 23:00 +0100
    Re: [PATCH 2/4] timer: relax tick stop in idle entry Thomas Gleixner <tglx@linutronix.de> - 2015-11-16 23:10 +0100
      Re: [PATCH 2/4] timer: relax tick stop in idle entry Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-17 01:20 +0100
        Re: [PATCH 2/4] timer: relax tick stop in idle entry Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-19 18:50 +0100
        Re: [PATCH 2/4] timer: relax tick stop in idle entry Peter Zijlstra <peterz@infradead.org> - 2015-11-19 20:10 +0100
          Re: [PATCH 2/4] timer: relax tick stop in idle entry Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-19 20:30 +0100
            Re: [PATCH 2/4] timer: relax tick stop in idle entry Peter Zijlstra <peterz@infradead.org> - 2015-11-19 21:00 +0100
              Re: [PATCH 2/4] timer: relax tick stop in idle entry Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-20 00:50 +0100
    Re: [PATCH 2/4] timer: relax tick stop in idle entry "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-11-16 23:40 +0100
      Re: [PATCH 2/4] timer: relax tick stop in idle entry Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-17 00:10 +0100
      Re: [PATCH 2/4] timer: relax tick stop in idle entry Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-17 00:20 +0100
        Re: [PATCH 2/4] timer: relax tick stop in idle entry "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-11-17 00:30 +0100
          Re: [PATCH 2/4] timer: relax tick stop in idle entry Arjan van de Ven <arjan@linux.intel.com> - 2015-11-17 00:40 +0100
            Re: [PATCH 2/4] timer: relax tick stop in idle entry Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-17 00:50 +0100
              Re: [PATCH 2/4] timer: relax tick stop in idle entry "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-11-17 01:10 +0100
    Re: [PATCH 2/4] timer: relax tick stop in idle entry Josh Triplett <josh@joshtriplett.org> - 2015-11-16 23:40 +0100
      Re: [PATCH 2/4] timer: relax tick stop in idle entry "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-11-17 00:30 +0100
        Re: [PATCH 2/4] timer: relax tick stop in idle entry Josh Triplett <josh@joshtriplett.org> - 2015-11-17 02:50 +0100
          Re: [PATCH 2/4] timer: relax tick stop in idle entry Arjan van de Ven <arjan@linux.intel.com> - 2015-11-17 04:00 +0100
            Re: [PATCH 2/4] timer: relax tick stop in idle entry "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-11-17 06:10 +0100
              Re: [PATCH 2/4] timer: relax tick stop in idle entry Peter Zijlstra <peterz@infradead.org> - 2015-11-17 11:30 +0100
                Re: [PATCH 2/4] timer: relax tick stop in idle entry Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-17 14:00 +0100
                Re: [PATCH 2/4] timer: relax tick stop in idle entry "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-11-17 14:50 +0100
          Re: [PATCH 2/4] timer: relax tick stop in idle entry "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-11-17 04:00 +0100

csiph-web