add nic afinity checks.

bin/system_info/print_system_info.c

@@ -46,8 +46,10 @@ int main(void) {
 
         const struct aws_string **nic_array = aws_system_environment_get_network_cards(env);
         for (size_t i = 0; i < nic_count; ++i) {
-            fprintf(stdout, "    '%s'", aws_string_c_str(nic_array[i]));
-
+            fprintf(stdout, "    {\n");
+            fprintf(stdout, "      'device_name: '%s',\n", aws_string_c_str(nic_array[i]));
+            fprintf(stdout, "      'numa_node: 'lu'\n", (unsigned long)aws_system_environment_get_cpu_group_for_network_card(env, i));
+            fprintf(stdout, "    }\n");
             if (i != nic_count - 1) {
                 fprintf(stdout, ",");
             }

include/aws/common/private/system_info_priv.h

@@ -15,6 +15,7 @@ struct aws_system_environment {
     struct aws_byte_buf virtualization_vendor;
     struct aws_byte_buf product_name;
     struct aws_array_list str_list_network_cards;
+    struct aws_array_list u16_nic_to_cpu_group;
     enum aws_platform_os os;
     size_t cpu_count;
     size_t cpu_group_count;

include/aws/common/system_info.h

@@ -64,6 +64,9 @@ size_t aws_system_environment_get_network_card_count(const struct aws_system_env
 AWS_COMMON_API
 const struct aws_string **aws_system_environment_get_network_cards(const struct aws_system_environment *env);
 
+AWS_COMMON_API
+uint16_t aws_system_environment_get_cpu_group_for_network_card(const struct aws_system_environment *env, size_t card_index);
+
 /**
  * Returns the number of processors for the specified compute environment.
  */

source/linux/system_info.c

@@ -21,16 +21,51 @@ int aws_system_environment_load_platform_impl(struct aws_system_environment *env
     aws_byte_buf_init_from_file_with_size_hint(
         &env->product_name, env->allocator, "/sys/devices/virtual/dmi/id/product_name", 32 /*size_hint*/);
 
+    /* iterate over network devices. */
     struct ifaddrs *addrs = NULL;
     struct ifaddrs *iterator = NULL;
 
     getifaddrs(&addrs);
     iterator = addrs;
-    
+
     while(iterator) {
         if (iterator->ifa_addr && iterator->ifa_addr->sa_family == AF_PACKET) {
             struct aws_string *device_name = aws_string_new_from_c_str(env->allocator, iterator->ifa_name);
             aws_array_list_push_back(&env->str_list_network_cards, &device_name);
+
+            /* figure out what numa node if any the network card is on. */
+            uint16_t group_id = 0;
+
+            struct aws_byte_buf temp_numa_info;
+            aws_byte_buf_init(&temp_numa_info, env->allocator, 256);
+            struct aws_byte_cursor initial_path = aws_byte_cursor_from_c_str("/sys/class/net/");
+            aws_byte_buf_write_from_whole_cursor(&temp_numa_info, initial_path);
+            struct aws_byte_cursor device_name_cur = aws_byte_cursor_from_string(device_name);
+            aws_byte_buf_append_dynamic(&temp_numa_info, &device_name_cur);
+            struct aws_byte_cursor final_path_segment = aws_byte_cursor_from_c_str("/device/numa_node");
+            aws_byte_buf_append_dynamic(&temp_numa_info, &final_path_segment);
+            /* add a null terminator for sys-call land. */
+            aws_byte_buf_append_byte_dynamic(&temp_numa_info, 0);
+
+            /* fill in buffer and read it converting to int. */
+            struct aws_byte_buf node_file;
+            AWS_ZERO_STRUCT(node_file);
+
+            if (aws_byte_buf_init_from_file(&node_file, env->allocator, (const char *)temp_numa_info.buffer) == AWS_OP_SUCCESS) {
+                struct aws_byte_cursor file_cur = aws_byte_cursor_from_buf(&temp_numa_info);
+
+                uint64_t parsed_int = 0;
+                if (aws_byte_cursor_utf8_parse_u64(file_cur, &parsed_int) == AWS_OP_SUCCESS) {
+
+                    /* should always be true, but doesn't hurt to be safe. */
+                    if (parsed_int < UINT16_MAX) {
+                        group_id = (uint16_t)parsed_int;
+                    }
+                }
+                aws_byte_buf_clean_up(&node_file);
+            }
+            aws_byte_buf_clean_up(&temp_numa_info);
+            aws_array_list_push_back(&env->u16_nic_to_cpu_group, &group_id);
         }
         iterator = iterator->ifa_next;
     }

source/system_info.c

@@ -12,6 +12,7 @@ void s_destroy_env(void *arg) {
     if (env) {
         aws_system_environment_destroy_platform_impl(env);
         aws_array_list_clean_up(&env->str_list_network_cards);
+        aws_array_list_clean_up(&env->u16_nic_to_cpu_group);
         aws_mem_release(env->allocator, env);
     }
 }
@@ -22,6 +23,7 @@ struct aws_system_environment *aws_system_environment_load(struct aws_allocator
     aws_ref_count_init(&env->ref_count, env, s_destroy_env);
 
     aws_array_list_init_dynamic(&env->str_list_network_cards, env->allocator, 2, sizeof(struct aws_string *));
+    aws_array_list_init_dynamic(&env->u16_nic_to_cpu_group, env->allocator, 2, sizeof(uint16_t));
 
     if (aws_system_environment_load_platform_impl(env)) {
         AWS_LOGF_ERROR(
@@ -89,3 +91,11 @@ size_t aws_system_environment_get_network_card_count(const struct aws_system_env
 const struct aws_string **aws_system_environment_get_network_cards(const struct aws_system_environment *env) {
     return env->str_list_network_cards.data;
 }
+
+uint16_t aws_system_environment_get_cpu_group_for_network_card(const struct aws_system_environment *env, size_t card_index) {
+    AWS_FATAL_ASSERT(card_index < aws_array_list_length(&env->u16_nic_to_cpu_group));
+
+    uint16_t value = 0;
+    aws_array_list_get_at(&env->u16_nic_to_cpu_group, &value, card_index);
+    return value;
+}