[PATCH tip/core/rcu 04/19] scftorture: Implement weighted primitive selection

paulmck
2020-08-31T18:09:42Z

This commit uses the scftorture.weight* kernel parameters to randomly
chooses between smp_call_function_single(), smp_call_function_many(),
and smp_call_function(). For each variant, it also randomly chooses
whether to invoke it synchronously (wait=1) or asynchronously (wait=0).
The percentage weighting for each option are dumped to the console log
(search for "scf_sel_dump").

This accumulates statistics, which a later commit will dump out at the
end of the run.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/scftorture.c | 182 ++++++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 155 insertions(+), 27 deletions(-)

diff --git a/kernel/scftorture.c b/kernel/scftorture.c
index 44f1e49..5f19845 100644
--- a/kernel/scftorture.c
+++ b/kernel/scftorture.c
@@ -64,8 +64,8 @@ torture_param(bool, use_cpus_read_lock, 0, "Use cpus_read_lock() to exclude CPU
torture_param(int, verbose, 0, "Enable verbose debugging printk()s");
torture_param(int, weight_single, -1, "Testing weight for single-CPU no-wait operations.");
torture_param(int, weight_single_wait, -1, "Testing weight for single-CPU operations.");
-torture_param(int, weight_mult, -1, "Testing weight for multi-CPU no-wait operations.");
-torture_param(int, weight_mult_wait, -1, "Testing weight for multi-CPU operations.");
+torture_param(int, weight_many, -1, "Testing weight for multi-CPU no-wait operations.");
+torture_param(int, weight_many_wait, -1, "Testing weight for multi-CPU operations.");
torture_param(int, weight_all, -1, "Testing weight for all-CPU no-wait operations.");
torture_param(int, weight_all_wait, -1, "Testing weight for all-CPU operations.");

@@ -83,9 +83,11 @@ struct scf_statistics {
struct task_struct *task;
int cpu;
long long n_single;
+ long long n_single_ofl;
long long n_single_wait;
- long long n_multi;
- long long n_multi_wait;
+ long long n_single_wait_ofl;
+ long long n_many;
+ long long n_many_wait;
long long n_all;
long long n_all_wait;
};
@@ -94,6 +96,27 @@ static struct scf_statistics *scf_stats_p;
static struct task_struct *scf_torture_stats_task;
static DEFINE_PER_CPU(long long, scf_invoked_count);

+// Data for random primitive selection
+#define SCF_PRIM_SINGLE 0
+#define SCF_PRIM_MANY 1
+#define SCF_PRIM_ALL 2
+#define SCF_NPRIMS (2 * 3) // Need wait and no-wait versions of each.
+
+static char *scf_prim_name[] = {
+ "smp_call_function_single",
+ "smp_call_function_many",
+ "smp_call_function",
+};
+
+struct scf_selector {
+ unsigned long scfs_weight;
+ int scfs_prim;
+ bool scfs_wait;
+};
+static struct scf_selector scf_sel_array[SCF_NPRIMS];
+static int scf_sel_array_len;
+static unsigned long scf_sel_totweight;
+
// Use to wait for all threads to start.
static atomic_t n_started;
static atomic_t n_errs;
@@ -131,6 +154,57 @@ scf_torture_stats(void *arg)
return 0;
}

+// Add a primitive to the scf_sel_array[].
+static void scf_sel_add(unsigned long weight, int prim, bool wait)
+{
+ struct scf_selector *scfsp = &scf_sel_array[scf_sel_array_len];
+
+ // If no weight, if array would overflow, if computing three-place
+ // percentages would overflow, or if the scf_prim_name[] array would
+ // overflow, don't bother. In the last three two cases, complain.
+ if (!weight ||
+ WARN_ON_ONCE(scf_sel_array_len >= ARRAY_SIZE(scf_sel_array)) ||
+ WARN_ON_ONCE(0 - 100000 * weight <= 100000 * scf_sel_totweight) ||
+ WARN_ON_ONCE(prim >= ARRAY_SIZE(scf_prim_name)))
+ return;
+ scf_sel_totweight += weight;
+ scfsp->scfs_weight = scf_sel_totweight;
+ scfsp->scfs_prim = prim;
+ scfsp->scfs_wait = wait;
+ scf_sel_array_len++;
+}
+
+// Dump out weighting percentages for scf_prim_name[] array.
+static void scf_sel_dump(void)
+{
+ int i;
+ unsigned long oldw = 0;
+ struct scf_selector *scfsp;
+ unsigned long w;
+
+ for (i = 0; i < scf_sel_array_len; i++) {
+ scfsp = &scf_sel_array[i];
+ w = (scfsp->scfs_weight - oldw) * 100000 / scf_sel_totweight;
+ pr_info("%s: %3lu.%03lu %s(%s)\n", __func__, w / 1000, w % 1000,
+ scf_prim_name[scfsp->scfs_prim],
+ scfsp->scfs_wait ? "wait" : "nowait");
+ oldw = scfsp->scfs_weight;
+ }
+}
+
+// Randomly pick a primitive and wait/nowait, based on weightings.
+static struct scf_selector *scf_sel_rand(struct torture_random_state *trsp)
+{
+ int i;
+ unsigned long w = torture_random(trsp) % (scf_sel_totweight + 1);
+
+ for (i = 0; i < scf_sel_array_len; i++)
+ if (scf_sel_array[i].scfs_weight >= w)
+ return &scf_sel_array[i];
+ WARN_ON_ONCE(1);
+ return &scf_sel_array[0];
+}
+
// Update statistics and occasionally burn up mass quantities of CPU time,
// if told to do so via scftorture.longwait. Otherwise, occasionally burn
// a little bit.
@@ -162,15 +236,55 @@ static void scf_handler(void *unused)
}
}

+// As above, but check for correct CPU.
+static void scf_handler_1(void *me)
+{
+ if (WARN_ON_ONCE(smp_processor_id() != (uintptr_t)me))
+ atomic_inc(&n_errs);
+ scf_handler(NULL);
+}
+
// Randomly do an smp_call_function*() invocation.
-static void scftorture_invoke_one(struct scf_statistics *scfp,struct torture_random_state *trsp)
+static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_random_state *trsp)
{
+ uintptr_t cpu;
+ int ret;
+ struct scf_selector *scfsp = scf_sel_rand(trsp);
+
if (use_cpus_read_lock)
cpus_read_lock();
else
preempt_disable();
- scfp->n_all++;
- smp_call_function(scf_handler, NULL, 0);
+ switch (scfsp->scfs_prim) {
+ case SCF_PRIM_SINGLE:
+ cpu = torture_random(trsp) % nr_cpu_ids;
+ if (scfsp->scfs_wait)
+ scfp->n_single_wait++;
+ else
+ scfp->n_single++;
+ ret = smp_call_function_single(cpu, scf_handler_1, (void *)cpu, scfsp->scfs_wait);
+ if (ret) {
+ if (scfsp->scfs_wait)
+ scfp->n_single_wait_ofl++;
+ else
+ scfp->n_single_ofl++;
+ }
+ break;
+ case SCF_PRIM_MANY:
+ if (scfsp->scfs_wait)
+ scfp->n_many_wait++;
+ else
+ scfp->n_many++;
+ smp_call_function_many(cpu_online_mask, scf_handler, NULL, scfsp->scfs_wait);
+ break;
+ case SCF_PRIM_ALL:
+ if (scfsp->scfs_wait)
+ scfp->n_all_wait++;
+ else
+ scfp->n_all++;
+ smp_call_function(scf_handler, NULL, scfsp->scfs_wait);
+ break;
+ }
if (use_cpus_read_lock)
cpus_read_unlock();
else
@@ -222,8 +336,8 @@ static void
scftorture_print_module_parms(const char *tag)
{
pr_alert(SCFTORT_FLAG
- "--- %s: verbose=%d holdoff=%d longwait=%d nthreads=%d onoff_holdoff=%d onoff_interval=%d shutdown_secs=%d stat_interval=%d stutter_cpus=%d use_cpus_read_lock=%d, weight_single=%d, weight_single_wait=%d, weight_mult=%d, weight_mult_wait=%d, weight_all=%d, weight_all_wait=%d\n", tag,
- verbose, holdoff, longwait, nthreads, onoff_holdoff, onoff_interval, shutdown, stat_interval, stutter_cpus, use_cpus_read_lock, weight_single, weight_single_wait, weight_mult, weight_mult_wait, weight_all, weight_all_wait);
+ "--- %s: verbose=%d holdoff=%d longwait=%d nthreads=%d onoff_holdoff=%d onoff_interval=%d shutdown_secs=%d stat_interval=%d stutter_cpus=%d use_cpus_read_lock=%d, weight_single=%d, weight_single_wait=%d, weight_many=%d, weight_many_wait=%d, weight_all=%d, weight_all_wait=%d\n", tag,
+ verbose, holdoff, longwait, nthreads, onoff_holdoff, onoff_interval, shutdown, stat_interval, stutter_cpus, use_cpus_read_lock, weight_single, weight_single_wait, weight_many, weight_many_wait, weight_all, weight_all_wait);
}

static void scf_cleanup_handler(void *unused)
@@ -264,6 +378,12 @@ static int __init scf_torture_init(void)
{
long i;
int firsterr = 0;
+ unsigned long weight_single1 = weight_single;
+ unsigned long weight_single_wait1 = weight_single_wait;
+ unsigned long weight_many1 = weight_many;
+ unsigned long weight_many_wait1 = weight_many_wait;
+ unsigned long weight_all1 = weight_all;
+ unsigned long weight_all_wait1 = weight_all_wait;

if (!torture_init_begin(SCFTORT_STRING, verbose))
return -EBUSY;
@@ -271,34 +391,42 @@ static int __init scf_torture_init(void)
scftorture_print_module_parms("Start of test");

if (weight_single == -1 && weight_single_wait == -1 &&
- weight_mult == -1 && weight_mult_wait == -1 &&
+ weight_many == -1 && weight_many_wait == -1 &&
weight_all == -1 && weight_all_wait == -1) {
- weight_single = 1;
- weight_single_wait = 1;
- weight_mult = 1;
- weight_mult_wait = 1;
- weight_all = 1;
- weight_all_wait = 1;
+ weight_single1 = 2 * nr_cpu_ids;
+ weight_single_wait1 = 2 * nr_cpu_ids;
+ weight_many1 = 2;
+ weight_many_wait1 = 2;
+ weight_all1 = 1;
+ weight_all_wait1 = 1;
} else {
if (weight_single == -1)
- weight_single = 0;
+ weight_single1 = 0;
if (weight_single_wait == -1)
- weight_single_wait = 0;
- if (weight_mult == -1)
- weight_mult = 0;
- if (weight_mult_wait == -1)
- weight_mult_wait = 0;
+ weight_single_wait1 = 0;
+ if (weight_many == -1)
+ weight_many1 = 0;
+ if (weight_many_wait == -1)
+ weight_many_wait1 = 0;
if (weight_all == -1)
- weight_all = 0;
+ weight_all1 = 0;
if (weight_all_wait == -1)
- weight_all_wait = 0;
+ weight_all_wait1 = 0;
}
- if (weight_single == 0 && weight_single_wait == 0 &&
- weight_mult == 0 && weight_mult_wait == 0 &&
- weight_all == 0 && weight_all_wait == 0) {
+ if (weight_single1 == 0 && weight_single_wait1 == 0 &&
+ weight_many1 == 0 && weight_many_wait1 == 0 &&
+ weight_all1 == 0 && weight_all_wait1 == 0) {
+ VERBOSE_SCFTORTOUT_ERRSTRING("all zero weights makes no sense");
firsterr = -EINVAL;
goto unwind;
}
+ scf_sel_add(weight_single1, SCF_PRIM_SINGLE, false);
+ scf_sel_add(weight_single_wait1, SCF_PRIM_SINGLE, true);
+ scf_sel_add(weight_many1, SCF_PRIM_MANY, false);
+ scf_sel_add(weight_many_wait1, SCF_PRIM_MANY, true);
+ scf_sel_add(weight_all1, SCF_PRIM_ALL, false);
+ scf_sel_add(weight_all_wait1, SCF_PRIM_ALL, true);
+ scf_sel_dump();

if (onoff_interval > 0) {
firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval, NULL);
--
2.9.5