opal/mca/ofi: select NIC closest to accelerator if requested

When accelerator is requested, select the closest NIC to the accelerator
device. If the accelerator or NIC PCI information is not available,
fallback to select the NIC on the closest package.

Signed-off-by: Wenduo Wang <wenduwan@amazon.com>

Author: wenduwan

opal/mca/common/ofi/common_ofi.c

@@ -30,6 +30,7 @@
 
 #include "common_ofi.h"
 #include "opal/constants.h"
+#include "opal/mca/accelerator/accelerator.h"
 #include "opal/mca/base/mca_base_framework.h"
 #include "opal/mca/base/mca_base_var.h"
 #include "opal/mca/hwloc/base/base.h"
@@ -38,6 +39,7 @@
 #include "opal/util/argv.h"
 #include "opal/util/show_help.h"
 
+extern opal_accelerator_base_module_t opal_accelerator;
 opal_common_ofi_module_t opal_common_ofi = {.prov_include = NULL,
                                             .prov_exclude = NULL,
                                             .output = -1};
@@ -915,15 +917,184 @@ static uint32_t get_package_rank(opal_process_info_t *process_info)
     return (uint32_t) process_info->myprocid.rank;
 }
 
+static int get_obj_depth(hwloc_obj_t obj, int *depth)
+{
+    hwloc_obj_t parent = NULL;
+    int depth_from_obj = 0;
+
+    /* For hwloc < 2.0, depth is unsigned type, but it could store a negative value */
+    if (0 <= (int) obj->depth) {
+        *depth = obj->depth;
+        return OPAL_SUCCESS;
+    }
+
+    parent = obj->parent;
+    while (parent) {
+        ++depth_from_obj;
+        if (0 <= (int) parent->depth) {
+            *depth = parent->depth + depth_from_obj;
+            return OPAL_SUCCESS;
+        }
+        parent = obj->parent;
+    }
+
+    return OPAL_ERROR;
+}
+
+#if OPAL_OFI_PCI_DATA_AVAILABLE
+/**
+ * @brief Attempt to find a nearest provider from the accelerator.
+ * Check if opal_accelerator is initialized with a valid PCI device, and find a provider from the
+ * shortest distance.
+ * Special cases:
+ * 1. If not accelerator device is available, returns OPAL_ERR_NOT_AVAILABLE.
+ * 2. If the provider does not have PCI attributers, we do not attempt to make a selection, and
+ *    return OPAL_ERR_NOT_AVAILABLE.
+ * 3. If there are more than 1 providers with the same equal distance, break the tie using a modulo
+ *    i.e. (local rank on the same accelerator) % (number of nearest providers)
+ * @param[in]   provider_list   linked list of providers
+ * @param[in]   num_providers   number of providers
+ * @param[in]   accl_id         Accelerator id
+ * @param[in]   device_rank     local rank on the accelerator
+ * @param[out]  provider        pointer to the selected provider
+ * @return      OPAL_SUCCESS if a provider is successfully selected
+ *              OPAL_ERR_NOT_AVAILABLE if a provider cannot be decided deterministically
+ *              OPAL_ERROR if a fatal error happened
+ */
+static int find_nearest_provider_from_accelerator(struct fi_info *provider_list,
+                                                  size_t num_providers,
+                                                  int accl_id,
+                                                  uint32_t device_rank,
+                                                  struct fi_info **provider)
+{
+    hwloc_obj_t accl_dev = NULL, prov_dev = NULL, common_ancestor = NULL;
+    int ret = -1, depth = -1, max_common_ancestor_depth = -1;
+    opal_accelerator_pci_attr_t accl_pci_attr = {0};
+    struct fi_info *current_provider = NULL;
+    struct fi_pci_attr pci = {0};
+    uint32_t near_provider_count = 0, provider_rank = 0;
+    uint32_t distances[num_providers], *distance = distances;
+
+    memset(distances, 0, sizeof(distances));
+
+    ret = opal_accelerator.get_device_pci_attr(accl_id, &accl_pci_attr);
+    if (OPAL_SUCCESS != ret) {
+        opal_output_verbose(1, opal_common_ofi.output,
+                            "%s:%d:Accelerator PCI info is not available", __FILE__, __LINE__);
+        return OPAL_ERROR;
+    }
+
+    accl_dev = hwloc_get_pcidev_by_busid(opal_hwloc_topology, accl_pci_attr.domain_id,
+                                         accl_pci_attr.bus_id, accl_pci_attr.device_id,
+                                         accl_pci_attr.function_id);
+    if (NULL == accl_dev) {
+        opal_output_verbose(1, opal_common_ofi.output,
+                            "%s:%d:Failed to find accelerator PCI device", __FILE__, __LINE__);
+        return OPAL_ERROR;
+    }
+
+    opal_output_verbose(1, opal_common_ofi.output,
+                        "%s:%d:Found accelerator device %d: %04x:%02x:%02x.%x VID: %x DID: %x",
+                        __FILE__, __LINE__, accl_id, accl_pci_attr.domain_id, accl_pci_attr.bus_id,
+                        accl_pci_attr.device_id, accl_pci_attr.function_id,
+                        accl_dev->attr->pcidev.vendor_id, accl_dev->attr->pcidev.device_id);
+
+    current_provider = provider_list;
+    while (NULL != current_provider) {
+        common_ancestor = NULL;
+        if (0 == check_provider_attr(provider_list, current_provider)
+            && OPAL_SUCCESS == get_provider_nic_pci(current_provider, &pci)) {
+            prov_dev = hwloc_get_pcidev_by_busid(opal_hwloc_topology, pci.domain_id, pci.bus_id,
+                                                 pci.device_id, pci.function_id);
+            if (NULL == prov_dev) {
+                opal_output_verbose(1, opal_common_ofi.output,
+                                    "%s:%d:Failed to find provider PCI device", __FILE__, __LINE__);
+                return OPAL_ERROR;
+            }
+
+            common_ancestor = hwloc_get_common_ancestor_obj(opal_hwloc_topology, accl_dev,
+                                                            prov_dev);
+            if (!common_ancestor) {
+                opal_output_verbose(
+                    1, opal_common_ofi.output,
+                    "%s:%d:Failed to find common ancestor of accelerator and provider PCI device",
+                    __FILE__, __LINE__);
+                /**
+                 * Return error because any 2 PCI devices should share at least one common ancestor,
+                 * i.e. root
+                 */
+                return OPAL_ERROR;
+            }
+
+            ret = get_obj_depth(common_ancestor, &depth);
+            if (OPAL_SUCCESS != ret) {
+                opal_output_verbose(1, opal_common_ofi.output,
+                                    "%s:%d:Failed to get common ancestor depth", __FILE__,
+                                    __LINE__);
+                return OPAL_ERROR;
+            }
+
+            if (max_common_ancestor_depth < depth) {
+                max_common_ancestor_depth = depth;
+                near_provider_count = 1;
+            } else if (max_common_ancestor_depth == depth) {
+                ++near_provider_count;
+            }
+        }
+
+        *(distance++) = !common_ancestor ? 0 : depth;
+        current_provider = current_provider->next;
+    }
+
+    if (0 == near_provider_count || 0 > max_common_ancestor_depth) {
+        opal_output_verbose(1, opal_common_ofi.output, "%s:%d:Provider does not have PCI device",
+                            __FILE__, __LINE__);
+        return OPAL_ERR_NOT_AVAILABLE;
+    }
+
+    provider_rank = device_rank % near_provider_count;
+
+    distance = distances;
+    current_provider = provider_list;
+    while (NULL != current_provider) {
+        if ((uint32_t) max_common_ancestor_depth == *(distance++)
+            && provider_rank == --near_provider_count) {
+            *provider = current_provider;
+            return OPAL_SUCCESS;
+        }
+
+        current_provider = current_provider->next;
+    }
+
+    assert(0 == near_provider_count);
+
+    return OPAL_ERROR;
+}
+#endif /* OPAL_OFI_PCI_DATA_AVAILABLE */
+
+
 struct fi_info *opal_common_ofi_select_provider(struct fi_info *provider_list,
                                                 opal_process_info_t *process_info)
 {
-    int ret, num_providers = 0;
+    int ret, num_providers = 0, accel_id = -1;
     struct fi_info *provider = NULL;
-    uint32_t package_rank = process_info->my_local_rank;
+    uint32_t package_rank;
 
+    /* Current process' local rank on the same package(socket) */
+    package_rank = process_info->proc_is_bound ? get_package_rank(process_info)
+                                               : process_info->my_local_rank;
     num_providers = count_providers(provider_list);
-    if (!process_info->proc_is_bound || 2 > num_providers) {
+
+#if OPAL_OFI_PCI_DATA_AVAILABLE
+    ret = opal_accelerator.get_device(&accel_id);
+    if (OPAL_SUCCESS != ret) {
+        opal_output_verbose(1, opal_common_ofi.output, "%s:%d:Accelerator is not available",
+                            __FILE__, __LINE__);
+        accel_id = -1;
+    }
+#endif /* OPAL_OFI_PCI_DATA_AVAILABLE */
+
+    if ((!process_info->proc_is_bound && 0 > accel_id) || 2 > num_providers) {
         goto round_robin;
     }
 
@@ -935,9 +1106,28 @@ struct fi_info *opal_common_ofi_select_provider(struct fi_info *provider_list,
                             __FILE__, __LINE__);
     }
 
-    package_rank = get_package_rank(process_info);
-
 #if OPAL_OFI_PCI_DATA_AVAILABLE
+    if (0 <= accel_id) {
+        /**
+         * If accelerator is enabled, select the closest provider to the accelerator.
+         * Note: the function expects a local rank on the accelerator to break ties if there are
+         * multiple equidistant providers. package_rank is NOT an accurate measure, but a proxy.
+         */
+        ret = find_nearest_provider_from_accelerator(provider_list, num_providers, accel_id,
+                                                     package_rank, &provider);
+        if (OPAL_SUCCESS == ret) {
+            goto out;
+        }
+
+        opal_output_verbose(1, opal_common_ofi.output,
+                            "%s:%d:Failed to find a provider close to the accelerator. Error: %d",
+                            __FILE__, __LINE__, ret);
+
+        if (!process_info->proc_is_bound) {
+            goto round_robin;
+        }
+    }
+
     /**
      * If provider PCI BDF information is available, we calculate its physical distance
      * to the current process, and select the provider with the shortest distance.