Re: [PATCH] rcu: Remove reduplicate check of cpu_online
On Wed, Feb 25, 2015 at 05:09:46PM +0800, Yao Dongdong wrote: > The calling function invoke_rcu_core will check it. > > Signed-off-by: Yao Dongdong Hmmm... That is a fastpath, but invoke_rcu_core() is visible to the compiler, which should inline anyway. I took this patch for 4.1, but updated the title and commit log as follows: rcu: Remove redundant check of cpu_online() Because invoke_cpu_core() checks whether the current CPU is online, there is no need for __call_rcu_core() to redundantly check it. There should not be any performance degradation because the called function is visible to the compiler. This commit therefore removes the redundant check. Thanx, Paul > --- > kernel/rcu/tree.c |2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 48d640c..e5f9b7e 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -2741,7 +2741,7 @@ static void __call_rcu_core(struct rcu_state *rsp, > struct rcu_data *rdp, >* If called from an extended quiescent state, invoke the RCU >* core in order to force a re-evaluation of RCU's idleness. >*/ > - if (!rcu_is_watching() && cpu_online(smp_processor_id())) > + if (!rcu_is_watching()) > invoke_rcu_core(); > > /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ > -- > 1.7.9.5 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] rcu: Remove reduplicate check of cpu_online
The calling function invoke_rcu_core will check it. Signed-off-by: Yao Dongdong --- kernel/rcu/tree.c |2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 48d640c..e5f9b7e 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2741,7 +2741,7 @@ static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp, * If called from an extended quiescent state, invoke the RCU * core in order to force a re-evaluation of RCU's idleness. */ - if (!rcu_is_watching() && cpu_online(smp_processor_id())) + if (!rcu_is_watching()) invoke_rcu_core(); /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] rcu: Remove reduplicate check of cpu_online
On Wed, Feb 25, 2015 at 05:09:46PM +0800, Yao Dongdong wrote: The calling function invoke_rcu_core will check it. Signed-off-by: Yao Dongdong yaodongd...@huawei.com Hmmm... That is a fastpath, but invoke_rcu_core() is visible to the compiler, which should inline anyway. I took this patch for 4.1, but updated the title and commit log as follows: rcu: Remove redundant check of cpu_online() Because invoke_cpu_core() checks whether the current CPU is online, there is no need for __call_rcu_core() to redundantly check it. There should not be any performance degradation because the called function is visible to the compiler. This commit therefore removes the redundant check. Thanx, Paul --- kernel/rcu/tree.c |2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 48d640c..e5f9b7e 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2741,7 +2741,7 @@ static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp, * If called from an extended quiescent state, invoke the RCU * core in order to force a re-evaluation of RCU's idleness. */ - if (!rcu_is_watching() cpu_online(smp_processor_id())) + if (!rcu_is_watching()) invoke_rcu_core(); /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ -- 1.7.9.5 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] rcu: Remove reduplicate check of cpu_online
The calling function invoke_rcu_core will check it. Signed-off-by: Yao Dongdong yaodongd...@huawei.com --- kernel/rcu/tree.c |2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 48d640c..e5f9b7e 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2741,7 +2741,7 @@ static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp, * If called from an extended quiescent state, invoke the RCU * core in order to force a re-evaluation of RCU's idleness. */ - if (!rcu_is_watching() cpu_online(smp_processor_id())) + if (!rcu_is_watching()) invoke_rcu_core(); /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ -- 1.7.9.5 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
