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Message-ID: <20130107205304.GV2525@linux.vnet.ibm.com>
Date: Mon, 7 Jan 2013 12:53:04 -0800
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Paul Gortmaker <paul.gortmaker@...driver.com>
Cc: linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
dipankar@...ibm.com, akpm@...ux-foundation.org,
mathieu.desnoyers@...ymtl.ca, josh@...htriplett.org,
niv@...ibm.com, tglx@...utronix.de, peterz@...radead.org,
rostedt@...dmis.org, Valdis.Kletnieks@...edu, dhowells@...hat.com,
edumazet@...gle.com, darren@...art.com, fweisbec@...il.com,
sbw@....edu, patches@...aro.org,
"Paul E. McKenney" <paul.mckenney@...aro.org>
Subject: Re: [PATCH tip/core/rcu 05/14] rcu: Distinguish "rcuo" kthreads by
RCU flavor
On Sun, Jan 06, 2013 at 06:34:17PM -0500, Paul Gortmaker wrote:
> On Sat, Jan 5, 2013 at 12:48 PM, Paul E. McKenney
> <paulmck@...ux.vnet.ibm.com> wrote:
> > From: "Paul E. McKenney" <paul.mckenney@...aro.org>
> >
> > Currently, the per-no-CBs-CPU kthreads are named "rcuo" followed by
> > the CPU number, for example, "rcuo". This is problematic given that
> > there are either two or three RCU flavors, each of which gets a per-CPU
> > kthread with exactly the same name. This commit therefore introduces
> > a one-letter abbreviation for each RCU flavor, namely 'b' for RCU-bh,
> > 'p' for RCU-preempt, and 's' for RCU-sched. This abbreviation use used
> > to distinguish the "rcuo" kthreads, for example, for CPU 0 we would have
> > "rcuo0b", "rcuo0p", and "rcuo0s".
>
> Since these names are exposed to Joe Average when he runs ps/top
> etc. -- I am inclined to favour the more full names as implemented
> in this older patch:
>
> http://goo.gl/H1Aj8
>
> ...since "rcuo0p" isn't apt to mean anything to people outside
> of the to/cc list of this mail. (Catch me off guard, and I probably
> might fail to be able to name the three flavours myself...)
>
> But then again it is just a personal preference. In any case, if we stick
> with the short names in your patch, we probably still should make the
> similar two documentation type chunks from my patch in yours.
I took yours and Josh's advice here, so the names are now rcuoX/N,
with the definitions of X and N in both the Kconfig entry and in
Documentation/kernel-parameters.txt.
Thanx, Paul
> Paul.
> --
>
> >
> > Signed-off-by: Paul E. McKenney <paul.mckenney@...aro.org>
> > Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> > Tested-by: Dietmar Eggemann <dietmar.eggemann@....com>
> > ---
> > kernel/rcutree.c | 7 ++++---
> > kernel/rcutree.h | 1 +
> > kernel/rcutree_plugin.h | 5 +++--
> > 3 files changed, 8 insertions(+), 5 deletions(-)
> >
> > diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> > index 8b110fa..4ec797e 100644
> > --- a/kernel/rcutree.c
> > +++ b/kernel/rcutree.c
> > @@ -64,7 +64,7 @@
> > static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
> > static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
> >
> > -#define RCU_STATE_INITIALIZER(sname, cr) { \
> > +#define RCU_STATE_INITIALIZER(sname, sabbr, cr) { \
> > .level = { &sname##_state.node[0] }, \
> > .call = cr, \
> > .fqs_state = RCU_GP_IDLE, \
> > @@ -76,13 +76,14 @@ static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
> > .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
> > .onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \
> > .name = #sname, \
> > + .abbr = sabbr, \
> > }
> >
> > struct rcu_state rcu_sched_state =
> > - RCU_STATE_INITIALIZER(rcu_sched, call_rcu_sched);
> > + RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
> > DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
> >
> > -struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, call_rcu_bh);
> > +struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh);
> > DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
> >
> > static struct rcu_state *rcu_state;
> > diff --git a/kernel/rcutree.h b/kernel/rcutree.h
> > index ef26eab..c865117 100644
> > --- a/kernel/rcutree.h
> > +++ b/kernel/rcutree.h
> > @@ -452,6 +452,7 @@ struct rcu_state {
> > unsigned long gp_max; /* Maximum GP duration in */
> > /* jiffies. */
> > char *name; /* Name of structure. */
> > + char abbr; /* Abbreviated name. */
> > struct list_head flavors; /* List of RCU flavors. */
> > };
> >
> > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
> > index eb9b473..ab1bdde 100644
> > --- a/kernel/rcutree_plugin.h
> > +++ b/kernel/rcutree_plugin.h
> > @@ -111,7 +111,7 @@ static void __init rcu_bootup_announce_oddness(void)
> > #ifdef CONFIG_TREE_PREEMPT_RCU
> >
> > struct rcu_state rcu_preempt_state =
> > - RCU_STATE_INITIALIZER(rcu_preempt, call_rcu);
> > + RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu);
> > DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data);
> > static struct rcu_state *rcu_state = &rcu_preempt_state;
> >
> > @@ -2510,7 +2510,8 @@ static void __init rcu_spawn_nocb_kthreads(struct rcu_state *rsp)
> > return;
> > for_each_cpu(cpu, rcu_nocb_mask) {
> > rdp = per_cpu_ptr(rsp->rda, cpu);
> > - t = kthread_run(rcu_nocb_kthread, rdp, "rcuo%d", cpu);
> > + t = kthread_run(rcu_nocb_kthread, rdp,
> > + "rcuo%d%c", cpu, rsp->abbr);
> > BUG_ON(IS_ERR(t));
> > ACCESS_ONCE(rdp->nocb_kthread) = t;
> > }
> > --
> > 1.7.8
> >
> > --
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