From: Frederic Weisbecker <frederic@kernel.org>
To: LKML <linux-kernel@vger.kernel.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Frederic Weisbecker <frederic@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Neeraj Upadhyay <neeraju@codeaurora.org>,
Joel Fernandes <joel@joelfernandes.org>,
Josh Triplett <josh@joshtriplett.org>
Subject: [PATCH 15/16] rcutorture: Test runtime toggling of CPUs' callback offloading
Date: Fri, 23 Oct 2020 16:46:48 +0200 [thread overview]
Message-ID: <20201023144649.53046-16-frederic@kernel.org> (raw)
In-Reply-To: <20201023144649.53046-1-frederic@kernel.org>
From: "Paul E. McKenney" <paulmck@kernel.org>
Frederic Weisbecker is adding the ability to change the rcu_nocbs state
of CPUs at runtime, that is, to offload and deoffload their RCU callback
processing without the need to reboot. As the old saying goes, "if it
ain't tested, it don't work", so this commit therefore adds prototype
rcutorture testing for this capability.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
---
.../admin-guide/kernel-parameters.txt | 8 ++
kernel/rcu/rcutorture.c | 86 ++++++++++++++++++-
kernel/rcu/tree_plugin.h | 3 +-
3 files changed, 93 insertions(+), 4 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 02d4adbf98d2..de31a867e0d9 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4324,6 +4324,14 @@
stress RCU, they don't participate in the actual
test, hence the "fake".
+ rcutorture.nocbs_nthreads= [KNL]
+ Set number of RCU callback-offload togglers.
+ Zero (the default) disables toggling.
+
+ rcutorture.nocbs_toggle= [KNL]
+ Set the delay in milliseconds between successive
+ callback-offload toggling attempts.
+
rcutorture.nreaders= [KNL]
Set number of RCU readers. The value -1 selects
N-1, where N is the number of CPUs. A value
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 916ea4f66e4b..c027b753bed5 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -97,6 +97,8 @@ torture_param(int, object_debug, 0,
torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
torture_param(int, onoff_interval, 0,
"Time between CPU hotplugs (jiffies), 0=disable");
+torture_param(int, nocbs_nthreads, 0, "Number of NOCB toggle threads, 0 to disable");
+torture_param(int, nocbs_toggle, 1000, "Time between toggling nocb state (ms)");
torture_param(int, read_exit_delay, 13,
"Delay between read-then-exit episodes (s)");
torture_param(int, read_exit_burst, 16,
@@ -127,10 +129,12 @@ static char *torture_type = "rcu";
module_param(torture_type, charp, 0444);
MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, srcu, ...)");
+static int nrealnocbers;
static int nrealreaders;
static struct task_struct *writer_task;
static struct task_struct **fakewriter_tasks;
static struct task_struct **reader_tasks;
+static struct task_struct **nocb_tasks;
static struct task_struct *stats_task;
static struct task_struct *fqs_task;
static struct task_struct *boost_tasks[NR_CPUS];
@@ -174,6 +178,8 @@ static unsigned long n_read_exits;
static struct list_head rcu_torture_removed;
static unsigned long shutdown_jiffies;
static unsigned long start_gp_seq;
+static atomic_long_t n_nocb_offload;
+static atomic_long_t n_nocb_deoffload;
static int rcu_torture_writer_state;
#define RTWS_FIXED_DELAY 0
@@ -1483,6 +1489,53 @@ rcu_torture_reader(void *arg)
return 0;
}
+/*
+ * Randomly Toggle CPUs' callback-offload state. This uses hrtimers to
+ * increase race probabilities and fuzzes the interval between toggling.
+ */
+static int rcu_nocb_toggle(void *arg)
+{
+ int cpu;
+ int maxcpu = -1;
+ int oldnice = task_nice(current);
+ long r;
+ DEFINE_TORTURE_RANDOM(rand);
+ ktime_t toggle_delay;
+ unsigned long toggle_fuzz;
+ ktime_t toggle_interval = ms_to_ktime(nocbs_toggle);
+
+ VERBOSE_TOROUT_STRING("rcu_nocb_toggle task started");
+ while (!rcu_inkernel_boot_has_ended())
+ schedule_timeout_interruptible(HZ / 10);
+ for_each_online_cpu(cpu)
+ maxcpu = cpu;
+ WARN_ON(maxcpu < 0);
+ if (toggle_interval > ULONG_MAX)
+ toggle_fuzz = ULONG_MAX >> 3;
+ else
+ toggle_fuzz = toggle_interval >> 3;
+ if (toggle_fuzz <= 0)
+ toggle_fuzz = NSEC_PER_USEC;
+ do {
+ r = torture_random(&rand);
+ cpu = (r >> 4) % (maxcpu + 1);
+ if (r & 0x1) {
+ rcu_nocb_cpu_offload(cpu);
+ atomic_long_inc(&n_nocb_offload);
+ } else {
+ rcu_nocb_cpu_deoffload(cpu);
+ atomic_long_inc(&n_nocb_deoffload);
+ }
+ toggle_delay = torture_random(&rand) % toggle_fuzz + toggle_interval;
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_hrtimeout(&toggle_delay, HRTIMER_MODE_REL);
+ if (stutter_wait("rcu_nocb_toggle"))
+ sched_set_normal(current, oldnice);
+ } while (!torture_must_stop());
+ torture_kthread_stopping("rcu_nocb_toggle");
+ return 0;
+}
+
/*
* Print torture statistics. Caller must ensure that there is only
* one call to this function at a given time!!! This is normally
@@ -1538,7 +1591,9 @@ rcu_torture_stats_print(void)
data_race(n_barrier_successes),
data_race(n_barrier_attempts),
data_race(n_rcu_torture_barrier_error));
- pr_cont("read-exits: %ld\n", data_race(n_read_exits));
+ pr_cont("read-exits: %ld ", data_race(n_read_exits));
+ pr_cont("nocb-toggles: %ld:%ld\n",
+ atomic_long_read(&n_nocb_offload), atomic_long_read(&n_nocb_deoffload));
pr_alert("%s%s ", torture_type, TORTURE_FLAG);
if (atomic_read(&n_rcu_torture_mberror) ||
@@ -1631,7 +1686,8 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
"stall_cpu_block=%d "
"n_barrier_cbs=%d "
"onoff_interval=%d onoff_holdoff=%d "
- "read_exit_delay=%d read_exit_burst=%d\n",
+ "read_exit_delay=%d read_exit_burst=%d "
+ "nocbs_nthreads=%d nocbs_toggle=%d\n",
torture_type, tag, nrealreaders, nfakewriters,
stat_interval, verbose, test_no_idle_hz, shuffle_interval,
stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
@@ -1641,7 +1697,8 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
stall_cpu_block,
n_barrier_cbs,
onoff_interval, onoff_holdoff,
- read_exit_delay, read_exit_burst);
+ read_exit_delay, read_exit_burst,
+ nocbs_nthreads, nocbs_toggle);
}
static int rcutorture_booster_cleanup(unsigned int cpu)
@@ -2479,6 +2536,13 @@ rcu_torture_cleanup(void)
torture_stop_kthread(rcu_torture_stall, stall_task);
torture_stop_kthread(rcu_torture_writer, writer_task);
+ if (nocb_tasks) {
+ for (i = 0; i < nrealnocbers; i++)
+ torture_stop_kthread(rcu_nocb_toggle, nocb_tasks[i]);
+ kfree(nocb_tasks);
+ nocb_tasks = NULL;
+ }
+
if (reader_tasks) {
for (i = 0; i < nrealreaders; i++)
torture_stop_kthread(rcu_torture_reader,
@@ -2742,6 +2806,22 @@ rcu_torture_init(void)
if (firsterr)
goto unwind;
}
+ nrealnocbers = nocbs_nthreads;
+ if (WARN_ON(nrealnocbers < 0))
+ nrealnocbers = 1;
+ if (WARN_ON(nocbs_toggle < 0))
+ nocbs_toggle = HZ;
+ nocb_tasks = kcalloc(nrealnocbers, sizeof(nocb_tasks[0]), GFP_KERNEL);
+ if (nocb_tasks == NULL) {
+ VERBOSE_TOROUT_ERRSTRING("out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
+ for (i = 0; i < nrealnocbers; i++) {
+ firsterr = torture_create_kthread(rcu_nocb_toggle, NULL, nocb_tasks[i]);
+ if (firsterr)
+ goto unwind;
+ }
if (stat_interval > 0) {
firsterr = torture_create_kthread(rcu_torture_stats, NULL,
stats_task);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 2f083beab9d9..5e0870229dd5 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2398,6 +2398,7 @@ int rcu_nocb_cpu_deoffload(int cpu)
return ret;
}
+EXPORT_SYMBOL_GPL(rcu_nocb_cpu_deoffload);
static int __rcu_nocb_rdp_offload(struct rcu_data *rdp)
{
@@ -2473,7 +2474,7 @@ int rcu_nocb_cpu_offload(int cpu)
return ret;
}
-
+EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload);
void __init rcu_init_nohz(void)
{
--
2.25.1
next prev parent reply other threads:[~2020-10-23 14:48 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-23 14:46 [PATCH 00/16] rcu/nocb: De-offload and re-offload support v3 Frederic Weisbecker
2020-10-23 14:46 ` [PATCH 01/16] rcu: Implement rcu_segcblist_is_offloaded() config dependent Frederic Weisbecker
2020-10-23 14:46 ` [PATCH 02/16] rcu: Turn enabled/offload states into a common flag Frederic Weisbecker
2020-10-23 14:46 ` [PATCH 03/16] rcu: Provide basic callback offloading state machine bits Frederic Weisbecker
2020-10-23 14:46 ` [PATCH 04/16] rcu/nocb: Always init segcblist on CPU up Frederic Weisbecker
2020-10-23 14:46 ` [PATCH 05/16] rcu: De-offloading CB kthread Frederic Weisbecker
2020-11-02 13:38 ` Boqun Feng
2020-11-04 14:31 ` Frederic Weisbecker
2020-11-04 14:42 ` Boqun Feng
2020-11-04 14:45 ` Frederic Weisbecker
2020-10-23 14:46 ` [PATCH 06/16] rcu/nocb: Don't deoffload an offline CPU with pending work Frederic Weisbecker
2020-10-23 14:46 ` [PATCH 07/16] rcu: De-offloading GP kthread Frederic Weisbecker
2020-10-23 14:46 ` [PATCH 08/16] rcu: Re-offload support Frederic Weisbecker
2020-10-23 14:46 ` [PATCH 09/16] rcu: Shutdown nocb timer on de-offloading Frederic Weisbecker
2020-10-23 14:46 ` [PATCH 10/16] rcu: Flush bypass before setting SEGCBLIST_SOFTIRQ_ONLY Frederic Weisbecker
2020-10-23 14:46 ` [PATCH 11/16] rcu: Set SEGCBLIST_SOFTIRQ_ONLY at the very last stage of de-offloading Frederic Weisbecker
2020-10-23 14:46 ` [PATCH 12/16] rcu/nocb: Only cond_resched() from actual offloaded batch processing Frederic Weisbecker
2020-10-23 14:46 ` [PATCH 13/16] rcu: Process batch locally as long as offloading isn't complete Frederic Weisbecker
2020-10-23 14:46 ` [PATCH 14/16] rcu: Locally accelerate callbacks " Frederic Weisbecker
2020-10-23 14:46 ` Frederic Weisbecker [this message]
2020-10-23 14:46 ` [PATCH 16/16] tools/rcutorture: Support nocb toggle in TREE01 Frederic Weisbecker
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20201023144649.53046-16-frederic@kernel.org \
--to=frederic@kernel.org \
--cc=jiangshanlai@gmail.com \
--cc=joel@joelfernandes.org \
--cc=josh@joshtriplett.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=neeraju@codeaurora.org \
--cc=paulmck@kernel.org \
--cc=rostedt@goodmis.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).