Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757943Ab2JKAuL (ORCPT ); Wed, 10 Oct 2012 20:50:11 -0400 Received: from e31.co.us.ibm.com ([32.97.110.149]:45377 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754435Ab2JKAuJ (ORCPT ); Wed, 10 Oct 2012 20:50:09 -0400 Date: Wed, 10 Oct 2012 17:50:04 -0700 From: "Paul E. McKenney" To: Frederic Weisbecker Cc: "Paul E. McKenney" , LKML Subject: Re: [PATCH] rcu: Advise most users not to enable RCU user mode Message-ID: <20121011005004.GL2495@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1349912908-11814-1-git-send-email-fweisbec@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1349912908-11814-1-git-send-email-fweisbec@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12101100-7282-0000-0000-00000DCD67C1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1796 Lines: 55 On Thu, Oct 11, 2012 at 01:48:28AM +0200, Frederic Weisbecker wrote: > Discourage distros from enabling CONFIG_RCU_USER_QS > because it brings overhead for no benefits yet. > > It's not a useful feature on its own until we can > fully run an adaptive tickless kernel. Queued, hopefully for 3.7, thank you! Thanx, Paul > Signed-off-by: Frederic Weisbecker > --- > init/Kconfig | 12 ++++++++++++ > 1 files changed, 12 insertions(+), 0 deletions(-) > > diff --git a/init/Kconfig b/init/Kconfig > index c26b8a1..89093e1 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -451,6 +451,12 @@ config RCU_USER_QS > excluded from the global RCU state machine and thus doesn't > to keep the timer tick on for RCU. > > + Unless you want to hack and help the development of the full > + tickless feature, you shouldn't enable this option. It adds > + unnecessary overhead. > + > + If unsure say N > + > config RCU_USER_QS_FORCE > bool "Force userspace extended QS by default" > depends on RCU_USER_QS > @@ -459,6 +465,12 @@ config RCU_USER_QS_FORCE > test this feature that treats userspace as an extended quiescent > state until we have a real user like a full adaptive nohz option. > > + Unless you want to hack and help the development of the full > + tickless feature, you shouldn't enable this option. It adds > + unnecessary overhead. > + > + If unsure say N > + > config RCU_FANOUT > int "Tree-based hierarchical RCU fanout value" > range 2 64 if 64BIT > -- > 1.7.5.4 > -- 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/