From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Josh Triplett <josh@joshtriplett.org>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu,
laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca,
niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, Valdis.Kletnieks@vt.edu,
dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com,
fweisbec@gmail.com, sbw@mit.edu, patches@linaro.org,
"Paul E. McKenney" <paul.mckenney@linaro.org>
Subject: Re: [PATCH tip/core/rcu 2/5] rcu: Track CPU-hotplug duration statistics
Date: Thu, 30 Aug 2012 13:38:42 -0700 [thread overview]
Message-ID: <20120830203842.GH30381@linux.vnet.ibm.com> (raw)
In-Reply-To: <20120830190017.GC6749@jtriplet-mobl1>
On Thu, Aug 30, 2012 at 12:00:18PM -0700, Josh Triplett wrote:
> On Thu, Aug 30, 2012 at 11:45:09AM -0700, Paul E. McKenney wrote:
> > From: "Paul E. McKenney" <paul.mckenney@linaro.org>
> >
> > Many rcutorture runs include CPU-hotplug operations in their stress
> > testing. This commit accumulates statistics on the durations of these
> > operations in deference to the recent concern about the overhead and
> > latency of these operations.
>
> How many jiffies, on average, do these operations take? Measuring these
> using jiffies seems highly prone to repeated rounding error.
On my laptop, 30-140 depending on what hotplug patches I have in place.
Some users have reported as few as 2-3 jiffies, but they don't use
rcutorture.
I eagerly look forward to the time when I need to change the timebase for
my own use. ;-)
Thanx, Paul
> > Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > ---
> > kernel/rcutorture.c | 42 +++++++++++++++++++++++++++++++++++++-----
> > 1 files changed, 37 insertions(+), 5 deletions(-)
> >
> > diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
> > index 86315d3..c6cf6ff 100644
> > --- a/kernel/rcutorture.c
> > +++ b/kernel/rcutorture.c
> > @@ -176,8 +176,14 @@ static long n_rcu_torture_boosts;
> > static long n_rcu_torture_timers;
> > static long n_offline_attempts;
> > static long n_offline_successes;
> > +static unsigned long sum_offline;
> > +static int min_offline = -1;
> > +static int max_offline;
> > static long n_online_attempts;
> > static long n_online_successes;
> > +static unsigned long sum_online;
> > +static int min_online = -1;
> > +static int max_online;
> > static long n_barrier_attempts;
> > static long n_barrier_successes;
> > static struct list_head rcu_torture_removed;
> > @@ -1214,11 +1220,13 @@ rcu_torture_printk(char *page)
> > n_rcu_torture_boost_failure,
> > n_rcu_torture_boosts,
> > n_rcu_torture_timers);
> > - cnt += sprintf(&page[cnt], "onoff: %ld/%ld:%ld/%ld ",
> > - n_online_successes,
> > - n_online_attempts,
> > - n_offline_successes,
> > - n_offline_attempts);
> > + cnt += sprintf(&page[cnt],
> > + "onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
> > + n_online_successes, n_online_attempts,
> > + n_offline_successes, n_offline_attempts,
> > + min_online, max_online,
> > + min_offline, max_offline,
> > + sum_online, sum_offline, HZ);
> > cnt += sprintf(&page[cnt], "barrier: %ld/%ld:%ld",
> > n_barrier_successes,
> > n_barrier_attempts,
> > @@ -1490,8 +1498,10 @@ static int __cpuinit
> > rcu_torture_onoff(void *arg)
> > {
> > int cpu;
> > + unsigned long delta;
> > int maxcpu = -1;
> > DEFINE_RCU_RANDOM(rand);
> > + unsigned long starttime;
> >
> > VERBOSE_PRINTK_STRING("rcu_torture_onoff task started");
> > for_each_online_cpu(cpu)
> > @@ -1509,6 +1519,7 @@ rcu_torture_onoff(void *arg)
> > printk(KERN_ALERT "%s" TORTURE_FLAG
> > "rcu_torture_onoff task: offlining %d\n",
> > torture_type, cpu);
> > + starttime = jiffies;
> > n_offline_attempts++;
> > if (cpu_down(cpu) == 0) {
> > if (verbose)
> > @@ -1516,12 +1527,23 @@ rcu_torture_onoff(void *arg)
> > "rcu_torture_onoff task: offlined %d\n",
> > torture_type, cpu);
> > n_offline_successes++;
> > + delta = jiffies - starttime;
> > + sum_offline += delta;
> > + if (min_offline < 0) {
> > + min_offline = delta;
> > + max_offline = delta;
> > + }
> > + if (min_offline > delta)
> > + min_offline = delta;
> > + if (max_offline < delta)
> > + max_offline = delta;
> > }
> > } else if (cpu_is_hotpluggable(cpu)) {
> > if (verbose)
> > printk(KERN_ALERT "%s" TORTURE_FLAG
> > "rcu_torture_onoff task: onlining %d\n",
> > torture_type, cpu);
> > + starttime = jiffies;
> > n_online_attempts++;
> > if (cpu_up(cpu) == 0) {
> > if (verbose)
> > @@ -1529,6 +1551,16 @@ rcu_torture_onoff(void *arg)
> > "rcu_torture_onoff task: onlined %d\n",
> > torture_type, cpu);
> > n_online_successes++;
> > + delta = jiffies - starttime;
> > + sum_online += delta;
> > + if (min_online < 0) {
> > + min_online = delta;
> > + max_online = delta;
> > + }
> > + if (min_online > delta)
> > + min_online = delta;
> > + if (max_online < delta)
> > + max_online = delta;
> > }
> > }
> > schedule_timeout_interruptible(onoff_interval * HZ);
> > --
> > 1.7.8
> >
>
next prev parent reply other threads:[~2012-08-30 20:48 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-30 18:44 [PATCH tip/core/rcu 0/5] Documentation and rcutorture changes Paul E. McKenney
2012-08-30 18:45 ` [PATCH tip/core/rcu 1/5] rcu: Update rcutorture defaults Paul E. McKenney
2012-08-30 18:45 ` [PATCH tip/core/rcu 2/5] rcu: Track CPU-hotplug duration statistics Paul E. McKenney
2012-08-30 19:00 ` Josh Triplett
2012-08-30 20:38 ` Paul E. McKenney [this message]
2012-08-30 23:23 ` Josh Triplett
2012-08-30 18:45 ` [PATCH tip/core/rcu 3/5] rcu: Document SRCU dead-CPU capabilities, emphasize read-side limits Paul E. McKenney
2012-08-30 19:01 ` Josh Triplett
2012-09-18 9:12 ` Lai Jiangshan
2012-09-18 23:32 ` Paul E. McKenney
2012-08-30 18:45 ` [PATCH tip/core/rcu 4/5] rcu: Switch rcutorture to pr_alert() and friends Paul E. McKenney
2012-08-30 19:05 ` Josh Triplett
2012-08-30 18:45 ` [PATCH tip/core/rcu 5/5] rcu: Prevent initialization race in rcutorture kthreads Paul E. McKenney
2012-08-30 19:15 ` Josh Triplett
2012-08-30 18:57 ` [PATCH tip/core/rcu 1/5] rcu: Update rcutorture defaults Josh Triplett
2012-08-30 21:35 ` Paul E. McKenney
2012-08-30 23:24 ` Josh Triplett
2012-08-30 18:56 ` [PATCH tip/core/rcu 0/5] Documentation and rcutorture changes Josh Triplett
2012-08-30 21:46 ` Paul E. McKenney
2012-08-30 23:22 ` Josh Triplett
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