Subject: Re: [PATCH 11/14] powerpc/64s: cpuidle read mostly for common globals

From: Vaidyanathan Srinivasan <[email-masked]>
Date: Mon, 12 Jun 2017 23:20:44 +0530

* Gautham R Shenoy <[email-masked]> [2017-06-12 21:00:27]:

> On Mon, Jun 12, 2017 at 09:58:32AM +1000, Nicholas Piggin wrote:
> > Ensure these don't get put into bouncing cachelines.
> > 
> > Signed-off-by: Nicholas Piggin <[email-masked]>
> 
> Reviewed-by: Gautham R. Shenoy <[email-masked]>
 
Reviewed-by: Vaidyanathan Srinivasan <[email-masked]>
 
> > ---
> >  drivers/cpuidle/cpuidle-powernv.c | 10 +++++-----
> >  drivers/cpuidle/cpuidle-pseries.c |  8 ++++----
> >  2 files changed, 9 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
> > index 50b3c2e0306f..9d03326ac05e 100644
> > --- a/drivers/cpuidle/cpuidle-powernv.c
> > +++ b/drivers/cpuidle/cpuidle-powernv.c
> > @@ -32,18 +32,18 @@ static struct cpuidle_driver powernv_idle_driver = {
> >  	.owner            = THIS_MODULE,
> >  };
> > 
> > -static int max_idle_state;
> > -static struct cpuidle_state *cpuidle_state_table;
> > +static int max_idle_state __read_mostly;
> > +static struct cpuidle_state *cpuidle_state_table __read_mostly;
> > 
> >  struct stop_psscr_table {
> >  	u64 val;
> >  	u64 mask;
> >  };
> > 
> > -static struct stop_psscr_table stop_psscr_table[CPUIDLE_STATE_MAX];
> > +static struct stop_psscr_table stop_psscr_table[CPUIDLE_STATE_MAX] __read_mostly;
> > 
> > -static u64 snooze_timeout;
> > -static bool snooze_timeout_en;
> > +static u64 snooze_timeout __read_mostly;
> > +static bool snooze_timeout_en __read_mostly;
> > 
> >  static int snooze_loop(struct cpuidle_device *dev,
> >  			struct cpuidle_driver *drv,
> > diff --git a/drivers/cpuidle/cpuidle-pseries.c b/drivers/cpuidle/cpuidle-pseries.c
> > index 7b12bb2ea70f..a404f352d284 100644
> > --- a/drivers/cpuidle/cpuidle-pseries.c
> > +++ b/drivers/cpuidle/cpuidle-pseries.c
> > @@ -25,10 +25,10 @@ struct cpuidle_driver pseries_idle_driver = {
> >  	.owner            = THIS_MODULE,
> >  };
> > 
> > -static int max_idle_state;
> > -static struct cpuidle_state *cpuidle_state_table;
> > -static u64 snooze_timeout;
> > -static bool snooze_timeout_en;
> > +static int max_idle_state __read_mostly;
> > +static struct cpuidle_state *cpuidle_state_table __read_mostly;
> > +static u64 snooze_timeout __read_mostly;
> > +static bool snooze_timeout_en __read_mostly;
> > 

Simple annotation of  __read_mostly could save us a few cache line
bounces.  Good idea.

--Vaidy