[PATCH 2/4] eal: allow applications to report their cpu usage

[Robin Jarry <rjarry@redhat.com>]

Allow applications to register a callback that will be invoked in
rte_lcore_dump() and when requesting lcore info in the telemetry API.

The callback is expected to return the number of TSC cycles that have
passed since application start and the number of these cycles that were
spent doing busy work.

Signed-off-by: Robin Jarry <rjarry@redhat.com>
Acked-by: Morten Brørup <mb@smartsharesystems.com>
---
v3 -> v4: Changed nomenclature: CPU cycles -> TSC cycles

 lib/eal/common/eal_common_lcore.c | 35 ++++++++++++++++++++++++++++---
 lib/eal/include/rte_lcore.h       | 29 +++++++++++++++++++++++++
 lib/eal/version.map               |  1 +
 3 files changed, 62 insertions(+), 3 deletions(-)

diff --git a/lib/eal/common/eal_common_lcore.c b/lib/eal/common/eal_common_lcore.c
index 16548977dce8..23717abf6530 100644
--- a/lib/eal/common/eal_common_lcore.c
+++ b/lib/eal/common/eal_common_lcore.c
@@ -2,6 +2,7 @@
  * Copyright(c) 2010-2014 Intel Corporation
  */
 
+#include <inttypes.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -422,11 +423,21 @@ rte_lcore_iterate(rte_lcore_iterate_cb cb, void *arg)
 	return ret;
 }
 
+static rte_lcore_usage_cb lcore_usage_cb;
+
+void
+rte_lcore_register_usage_cb(rte_lcore_usage_cb cb)
+{
+	lcore_usage_cb = cb;
+}
+
 static int
 lcore_dump_cb(unsigned int lcore_id, void *arg)
 {
 	struct rte_config *cfg = rte_eal_get_configuration();
-	char cpuset[RTE_CPU_AFFINITY_STR_LEN];
+	char cpuset[RTE_CPU_AFFINITY_STR_LEN], usage_str[256];
+	uint64_t busy_cycles, total_cycles;
+	rte_lcore_usage_cb usage_cb;
 	const char *role;
 	FILE *f = arg;
 	int ret;
@@ -446,11 +457,20 @@ lcore_dump_cb(unsigned int lcore_id, void *arg)
 		break;
 	}
 
+	busy_cycles = 0;
+	total_cycles = 0;
+	usage_str[0] = '\0';
+	usage_cb = lcore_usage_cb;
+	if (usage_cb != NULL && usage_cb(lcore_id, &busy_cycles, &total_cycles) == 0) {
+		snprintf(usage_str, sizeof(usage_str), ", busy cycles %"PRIu64"/%"PRIu64,
+			busy_cycles, total_cycles);
+	}
 	ret = eal_thread_dump_affinity(&lcore_config[lcore_id].cpuset, cpuset,
 		sizeof(cpuset));
-	fprintf(f, "lcore %u, socket %u, role %s, cpuset %s%s\n", lcore_id,
+	fprintf(f, "lcore %u, socket %u, role %s, cpuset %s%s%s\n", lcore_id,
 		rte_lcore_to_socket_id(lcore_id), role, cpuset,
-		ret == 0 ? "" : "...");
+		ret == 0 ? "" : "...", usage_str);
+
 	return 0;
 }
 
@@ -489,7 +509,9 @@ lcore_telemetry_info_cb(unsigned int lcore_id, void *arg)
 {
 	struct lcore_telemetry_info *info = arg;
 	struct rte_config *cfg = rte_eal_get_configuration();
+	uint64_t busy_cycles, total_cycles;
 	struct rte_tel_data *cpuset;
+	rte_lcore_usage_cb usage_cb;
 	const char *role;
 	unsigned int cpu;
 
@@ -522,6 +544,13 @@ lcore_telemetry_info_cb(unsigned int lcore_id, void *arg)
 		if (CPU_ISSET(cpu, &lcore_config[lcore_id].cpuset))
 			rte_tel_data_add_array_int(cpuset, cpu);
 	rte_tel_data_add_dict_container(info->d, "cpuset", cpuset, 0);
+	busy_cycles = 0;
+	total_cycles = 0;
+	usage_cb = lcore_usage_cb;
+	if (usage_cb != NULL && usage_cb(lcore_id, &busy_cycles, &total_cycles) == 0) {
+		rte_tel_data_add_dict_u64(info->d, "busy_cycles", busy_cycles);
+		rte_tel_data_add_dict_u64(info->d, "total_cycles", total_cycles);
+	}
 
 	return 0;
 }
diff --git a/lib/eal/include/rte_lcore.h b/lib/eal/include/rte_lcore.h
index 6938c3fd7b81..df7f0a8e07c6 100644
--- a/lib/eal/include/rte_lcore.h
+++ b/lib/eal/include/rte_lcore.h
@@ -328,6 +328,35 @@ typedef int (*rte_lcore_iterate_cb)(unsigned int lcore_id, void *arg);
 int
 rte_lcore_iterate(rte_lcore_iterate_cb cb, void *arg);
 
+/**
+ * Callback to allow applications to report CPU usage.
+ *
+ * @param [in] lcore_id
+ *   The lcore to consider.
+ * @param [out] busy_cycles
+ *   The amount of busy time since application start, in TSC cycles.
+ * @param [out] total_cycles
+ *   The total amount of time since application start, in TSC cycles.
+ * @return
+ *   - 0 if both busy and total were set correctly.
+ *   - a negative value if the information is not available or if any error occurred.
+ */
+typedef int (*rte_lcore_usage_cb)(
+	unsigned int lcore_id, uint64_t *busy_cycles, uint64_t *total_cycles);
+
+/**
+ * Register a callback from an application to be called in rte_lcore_dump()
+ * and the /eal/lcore/info telemetry endpoint handler.
+ *
+ * Applications are expected to report the amount of busy and total TSC cycles
+ * since their startup.
+ *
+ * @param cb
+ *   The callback function.
+ */
+__rte_experimental
+void rte_lcore_register_usage_cb(rte_lcore_usage_cb cb);
+
 /**
  * List all lcores.
  *
diff --git a/lib/eal/version.map b/lib/eal/version.map
index 7ad12a7dc985..30fd216a12ea 100644
--- a/lib/eal/version.map
+++ b/lib/eal/version.map
@@ -440,6 +440,7 @@ EXPERIMENTAL {
 	rte_thread_detach;
 	rte_thread_equal;
 	rte_thread_join;
+	rte_lcore_register_usage_cb;
 };
 
 INTERNAL {
-- 
2.38.1