Messages in this thread | | | Date | Thu, 8 Mar 2012 11:14:39 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 2/6] Don't touch the snap in srcu_readers_active() |
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On Tue, Mar 06, 2012 at 05:57:34PM +0800, Lai Jiangshan wrote: > srcu_readers_active() is called without the mutex, but it touch the snap. > also achieve better cache locality a little > > Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Queued with updated commit-log message, thank you!
Thanx, Paul
Expand the calls to srcu_readers_active_idx() from srcu_readers_active() inline. This change improves cache locality by interating over the CPUs once rather than twice.
> --- > kernel/srcu.c | 9 ++++++++- > 1 files changed, 8 insertions(+), 1 deletions(-) > > diff --git a/kernel/srcu.c b/kernel/srcu.c > index b6b9ea2..fbe2d5f 100644 > --- a/kernel/srcu.c > +++ b/kernel/srcu.c > @@ -181,7 +181,14 @@ static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx) > */ > static int srcu_readers_active(struct srcu_struct *sp) > { > - return srcu_readers_active_idx(sp, 0) + srcu_readers_active_idx(sp, 1); > + int cpu; > + unsigned long sum = 0; > + > + for_each_possible_cpu(cpu) { > + sum += ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[0]); > + sum += ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[1]); > + } > + return sum & SRCU_REF_MASK; > } > > /** > -- > 1.7.4.4 >
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