Messages in this thread | | | Date | Tue, 21 May 2013 14:09:57 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH tip/core/rcu 13/13] rcu: Shrink TINY_RCU by reworking CPU-stall ifdefs |
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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" <paulmck@linux.vnet.ibm.com> > > > > 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 <paulmck@linux.vnet.ibm.com> > > 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/ >
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