From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753769Ab3EUVKt (ORCPT ); Tue, 21 May 2013 17:10:49 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:60265 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751953Ab3EUVKs (ORCPT ); Tue, 21 May 2013 17:10:48 -0400 Date: Tue, 21 May 2013 14:09:57 -0700 From: "Paul E. McKenney" To: Josh Triplett Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu Subject: Re: [PATCH tip/core/rcu 13/13] rcu: Shrink TINY_RCU by reworking CPU-stall ifdefs Message-ID: <20130521210957.GV3578@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20130520145751.GA32218@linux.vnet.ibm.com> <1369061900-546-1-git-send-email-paulmck@linux.vnet.ibm.com> <1369061900-546-13-git-send-email-paulmck@linux.vnet.ibm.com> <20130521173140.GA3878@jtriplet-mobl1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130521173140.GA3878@jtriplet-mobl1> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13052121-5518-0000-0000-00000EE29E6E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 21, 2013 at 10:31:41AM -0700, Josh Triplett wrote: > On Mon, May 20, 2013 at 07:58:20AM -0700, Paul E. McKenney wrote: > > From: "Paul E. McKenney" > > > > TINY_RCU's reset_cpu_stall_ticks() and check_cpu_stalls() functions > > are defined unconditionally, and are empty functions if CONFIG_RCU_TRACE > > is disabled (which in turns disables detection of RCU CPU stalls). > > These empty functions can add a bit of bloat to TINY_RCU, so this > > commit reworks the ifdefs so that these functions are defined only > > if they actually do something. > > > > Signed-off-by: Paul E. McKenney > > Strange. Both of these functions are static, and called in only one > place, so shouldn't the compiler inline them (and thus throw them away > completely when empty)? Why does it not do so? Good point for most architectures. But given Tiny RCU's purpose, it should allow for stupid compilers. And I do need to fix the commit message to call out the other benefit, namely saving a couple of lines of source code. Thanx, Paul > - Josh Triplett > > > --- > > kernel/rcutiny.c | 4 ++-- > > kernel/rcutiny_plugin.h | 6 ++---- > > 2 files changed, 4 insertions(+), 6 deletions(-) > > > > diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c > > index 4adc9e2..aa34411 100644 > > --- a/kernel/rcutiny.c > > +++ b/kernel/rcutiny.c > > @@ -204,7 +204,7 @@ static int rcu_is_cpu_rrupt_from_idle(void) > > */ > > static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) > > { > > - reset_cpu_stall_ticks(rcp); > > + RCU_TRACE(reset_cpu_stall_ticks(rcp)); > > if (rcp->rcucblist != NULL && > > rcp->donetail != rcp->curtail) { > > rcp->donetail = rcp->curtail; > > @@ -251,7 +251,7 @@ void rcu_bh_qs(int cpu) > > */ > > void rcu_check_callbacks(int cpu, int user) > > { > > - check_cpu_stalls(); > > + RCU_TRACE(check_cpu_stalls()); > > if (user || rcu_is_cpu_rrupt_from_idle()) > > rcu_sched_qs(cpu); > > else if (!in_softirq()) > > diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h > > index 65ef180..0cd385a 100644 > > --- a/kernel/rcutiny_plugin.h > > +++ b/kernel/rcutiny_plugin.h > > @@ -158,15 +158,11 @@ static void check_cpu_stall(struct rcu_ctrlblk *rcp) > > rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check(); > > } > > > > -#endif /* #ifdef CONFIG_RCU_TRACE */ > > - > > static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp) > > { > > -#ifdef CONFIG_RCU_TRACE > > rcp->ticks_this_gp = 0; > > rcp->gp_start = jiffies; > > rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check(); > > -#endif /* #ifdef CONFIG_RCU_TRACE */ > > } > > > > static void check_cpu_stalls(void) > > @@ -174,3 +170,5 @@ static void check_cpu_stalls(void) > > RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk)); > > RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk)); > > } > > + > > +#endif /* #ifdef CONFIG_RCU_TRACE */ > > -- > > 1.8.1.5 > > > -- > 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/ >