[dpdk-dev] [PATCH v3 1/2] test/test: introduce new test-case for rte_smp_mb()

[Konstantin Ananyev <konstantin.ananyev@intel.com>]

Simple functional test for rte_smp_mb() implementations.
Also when executed on a single lcore could be used as rough
estimation how many cycles particular implementation of rte_smp_mb()
might take.

Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
---
 test/test/Makefile       |   1 +
 test/test/test_barrier.c | 286 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 287 insertions(+)
 create mode 100644 test/test/test_barrier.c

diff --git a/test/test/Makefile b/test/test/Makefile
index e7818dc6e..80fb09e2e 100644
--- a/test/test/Makefile
+++ b/test/test/Makefile
@@ -67,6 +67,7 @@ SRCS-y += test_spinlock.c
 SRCS-y += test_memory.c
 SRCS-y += test_memzone.c
 SRCS-y += test_bitmap.c
+SRCS-y += test_barrier.c
 
 SRCS-y += test_ring.c
 SRCS-y += test_ring_perf.c
diff --git a/test/test/test_barrier.c b/test/test/test_barrier.c
new file mode 100644
index 000000000..82b572c3e
--- /dev/null
+++ b/test/test/test_barrier.c
@@ -0,0 +1,286 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2010-2018 Intel Corporation
+ */
+
+ /*
+  * This is a simple functional test for rte_smp_mb() implementation.
+  * I.E. make sure that LOAD and STORE operations that precede the
+  * rte_smp_mb() call are globally visible across the lcores
+  * before the the LOAD and STORE operations that follows it.
+  * The test uses simple implementation of Peterson's lock algorithm
+  * (https://en.wikipedia.org/wiki/Peterson%27s_algorithm)
+  * for two execution units to make sure that rte_smp_mb() prevents
+  * store-load reordering to happen.
+  * Also when executed on a single lcore could be used as a approxiamate
+  * estimation of number of cycles particular implementation of rte_smp_mb()
+  * will take.
+  */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+#include <inttypes.h>
+
+#include <rte_memory.h>
+#include <rte_per_lcore.h>
+#include <rte_launch.h>
+#include <rte_atomic.h>
+#include <rte_eal.h>
+#include <rte_lcore.h>
+#include <rte_pause.h>
+#include <rte_random.h>
+#include <rte_cycles.h>
+#include <rte_vect.h>
+#include <rte_debug.h>
+
+#include "test.h"
+
+#define ADD_MAX		8
+#define ITER_MAX	0x1000000
+
+enum plock_use_type {
+	USE_MB,
+	USE_SMP_MB,
+	USE_NUM
+};
+
+struct plock {
+	volatile uint32_t flag[2];
+	volatile uint32_t victim;
+	enum plock_use_type utype;
+};
+
+/*
+ * Lock plus protected by it two counters.
+ */
+struct plock_test {
+	struct plock lock;
+	uint32_t val;
+	uint32_t iter;
+};
+
+/*
+ * Each active lcore shares plock_test struct with it's left and right
+ * neighbours.
+ */
+struct lcore_plock_test {
+	struct plock_test *pt[2]; /* shared, lock-protected data */
+	uint32_t sum[2];          /* local copy of the shared data */
+	uint32_t iter;            /* number of iterations to perfom */
+	uint32_t lc;              /* given lcore id */
+};
+
+static inline void
+store_load_barrier(uint32_t utype)
+{
+	if (utype == USE_MB)
+		rte_mb();
+	else if (utype == USE_SMP_MB)
+		rte_smp_mb();
+	else
+		RTE_VERIFY(0);
+}
+
+/*
+ * Peterson lock implementation.
+ */
+static void
+plock_lock(struct plock *l, uint32_t self)
+{
+	uint32_t other;
+
+	other = self ^ 1;
+
+	l->flag[self] = 1;
+	l->victim = self;
+
+	store_load_barrier(l->utype);
+
+	while (l->flag[other] == 1 && l->victim == self)
+		rte_pause();
+}
+
+static void
+plock_unlock(struct plock *l, uint32_t self)
+{
+	rte_smp_wmb();
+	l->flag[self] = 0;
+}
+
+static void
+plock_reset(struct plock *l, enum plock_use_type utype)
+{
+	memset(l, 0, sizeof(*l));
+	l->utype = utype;
+}
+
+/*
+ * grab the lock, update both counters, release the lock.
+ */
+static void
+plock_add(struct plock_test *pt, uint32_t self, uint32_t n)
+{
+	plock_lock(&pt->lock, self);
+	pt->iter++;
+	pt->val += n;
+	plock_unlock(&pt->lock, self);
+}
+
+static int
+plock_test1_lcore(void *data)
+{
+	uint64_t tm;
+	uint32_t i, lc, ln, n;
+	struct lcore_plock_test *lpt;
+
+	lpt = data;
+	lc = rte_lcore_id();
+
+	/* find lcore_plock_test struct for given lcore */
+	for (ln = rte_lcore_count(); ln != 0 && lpt->lc != lc; lpt++, ln--)
+		;
+
+	if (ln == 0) {
+		printf("%s(%u) error at init\n", __func__, lc);
+		return -1;
+	}
+
+	n = rte_rand() % ADD_MAX;
+	tm = rte_get_timer_cycles();
+
+	/*
+	 * for each iteration:
+	 * - update shared, locked protected data in a safe manner
+	 * - update local copy of the shared data
+	 */
+	for (i = 0; i != lpt->iter; i++) {
+
+		plock_add(lpt->pt[0], 0, n);
+		plock_add(lpt->pt[1], 1, n);
+
+		lpt->sum[0] += n;
+		lpt->sum[1] += n;
+
+		n = (n + 1) % ADD_MAX;
+	}
+
+	tm = rte_get_timer_cycles() - tm;
+
+	printf("%s(%u): %u iterations finished, in %" PRIu64
+		" cycles, %#Lf cycles/iteration, "
+		"local sum={%u, %u}\n",
+		__func__, lc, i, tm, (long double)tm / i,
+		lpt->sum[0], lpt->sum[1]);
+	return 0;
+}
+
+/*
+ * For N active lcores we allocate N+1 lcore_plock_test structures.
+ * Each active lcore shares one lcore_plock_test structure with its
+ * left lcore neighbor and one lcore_plock_test structure with its
+ * right lcore neighbor.
+ * During the test each lcore updates data in both shared structures and
+ * its local copies. Then at validation phase we check that our shared
+ * and local data are the same.
+ */
+static int
+plock_test(uint32_t iter, enum plock_use_type utype)
+{
+	int32_t rc;
+	uint32_t i, lc, n;
+	uint32_t *sum;
+	struct plock_test *pt;
+	struct lcore_plock_test *lpt;
+
+	/* init phase, allocate and initialize shared data */
+
+	n = rte_lcore_count();
+	pt = calloc(n + 1, sizeof(*pt));
+	lpt = calloc(n, sizeof(*lpt));
+	sum = calloc(n + 1, sizeof(*sum));
+
+	printf("%s(iter=%u, utype=%u) started on %u lcores\n",
+		__func__, iter, utype, n);
+
+	if (pt == NULL || lpt == NULL) {
+		printf("%s: failed to allocate memory for %u lcores\n",
+			__func__, n);
+		free(pt);
+		free(lpt);
+		free(sum);
+		return -ENOMEM;
+	}
+
+	for (i = 0; i != n + 1; i++)
+		plock_reset(&pt[i].lock, utype);
+
+	i = 0;
+	RTE_LCORE_FOREACH(lc) {
+
+		lpt[i].lc = lc;
+		lpt[i].iter = iter;
+		lpt[i].pt[0] = pt + i;
+		lpt[i].pt[1] = pt + i + 1;
+		i++;
+	}
+
+	lpt[i - 1].pt[1] = pt;
+
+	for (i = 0; i != n; i++)
+		printf("lpt[%u]={lc=%u, pt={%p, %p},};\n",
+			i, lpt[i].lc, lpt[i].pt[0], lpt[i].pt[1]);
+
+
+	/* test phase - start and wait for completion on each active lcore */
+
+	rte_eal_mp_remote_launch(plock_test1_lcore, lpt, CALL_MASTER);
+	rte_eal_mp_wait_lcore();
+
+	/* validation phase - make sure that shared and local data match */
+
+	for (i = 0; i != n; i++) {
+		sum[i] += lpt[i].sum[0];
+		sum[i + 1] += lpt[i].sum[1];
+	}
+
+	sum[0] += sum[i];
+
+	rc = 0;
+	for (i = 0; i != n; i++) {
+		printf("%s: sum[%u]=%u, pt[%u].val=%u, pt[%u].iter=%u;\n",
+			__func__, i, sum[i], i, pt[i].val, i, pt[i].iter);
+
+		/* race condition occurred, lock doesn't work properly */
+		if (sum[i] != pt[i].val || 2 * iter != pt[i].iter) {
+			printf("error: local and shared sums don't much\n");
+			rc = -1;
+		}
+	}
+
+	free(pt);
+	free(lpt);
+	free(sum);
+
+	printf("%s(utype=%u) returns %d\n", __func__, utype, rc);
+	return rc;
+}
+
+static int
+test_barrier(void)
+{
+	int32_t i, ret, rc[USE_NUM];
+
+	for (i = 0; i != RTE_DIM(rc); i++)
+		rc[i] = plock_test(ITER_MAX, i);
+
+	ret = 0;
+	for (i = 0; i != RTE_DIM(rc); i++) {
+		printf("%s for utype=%d %s\n",
+			__func__, i, rc[i] == 0 ? "passed" : "failed");
+		ret |= rc[i];
+	}
+
+	return ret;
+}
+
+REGISTER_TEST_COMMAND(barrier_autotest, test_barrier);
-- 
2.13.6