From 434c9055ee9bc2d951148def8e9fd2b2dba3b6fc Mon Sep 17 00:00:00 2001
From: Joseph Schuchart <schuchart@hlrs.de>
Date: Fri, 3 Apr 2020 12:03:17 +0200
Subject: [PATCH] UCX osc: fall back to get-compare-put for unsupported
 datatypes

Signed-off-by: Joseph Schuchart <schuchart@hlrs.de>
---
 ompi/mca/osc/ucx/osc_ucx_comm.c  | 81 +++++++++++++++++++++++++-------
 opal/mca/common/ucx/common_ucx.h |  2 +-
 2 files changed, 64 insertions(+), 19 deletions(-)

diff --git a/ompi/mca/osc/ucx/osc_ucx_comm.c b/ompi/mca/osc/ucx/osc_ucx_comm.c
index 6bafc4ea0b..46ce011599 100644
--- a/ompi/mca/osc/ucx/osc_ucx_comm.c
+++ b/ompi/mca/osc/ucx/osc_ucx_comm.c
@@ -722,6 +722,36 @@ int ompi_osc_ucx_accumulate(const void *origin_addr, int origin_count,
                           target_disp, target_count, target_dt, op, win, NULL);
 }
 
+static int
+do_atomic_compare_and_swap(const void *origin_addr, const void *compare_addr,
+                           void *result_addr, struct ompi_datatype_t *dt,
+                           int target, uint64_t remote_addr,
+                           ompi_osc_ucx_module_t *module)
+{
+    int ret;
+    bool lock_acquired = false;
+    size_t dt_bytes;
+    if (!module->acc_single_intrinsic) {
+        ret = start_atomicity(module, target, &lock_acquired);
+        if (ret != OMPI_SUCCESS) {
+            return ret;
+        }
+    }
+
+    ompi_datatype_type_size(dt, &dt_bytes);
+    uint64_t compare_val = opal_common_ucx_load_uint64(compare_addr, dt_bytes);
+    uint64_t value       = opal_common_ucx_load_uint64(origin_addr,  dt_bytes);
+    ret = opal_common_ucx_wpmem_cmpswp_nb(module->mem, compare_val, value, target,
+                                          result_addr, dt_bytes, remote_addr,
+                                          NULL, NULL);
+
+    if (module->acc_single_intrinsic) {
+        return ret;
+    }
+
+    return end_atomicity(module, target, lock_acquired, NULL);
+}
+
 int ompi_osc_ucx_compare_and_swap(const void *origin_addr, const void *compare_addr,
                                   void *result_addr, struct ompi_datatype_t *dt,
                                   int target, ptrdiff_t target_disp,
@@ -732,23 +762,11 @@ int ompi_osc_ucx_compare_and_swap(const void *origin_addr, const void *compare_a
     int ret = OMPI_SUCCESS;
     bool lock_acquired = false;
 
-    ompi_datatype_type_size(dt, &dt_bytes);
-    if (sizeof(uint64_t) < dt_bytes) {
-        return OMPI_ERR_NOT_SUPPORTED;
-    }
-
     ret = check_sync_state(module, target, false);
     if (ret != OMPI_SUCCESS) {
         return ret;
     }
 
-    if (!module->acc_single_intrinsic) {
-        ret = start_atomicity(module, target, &lock_acquired);
-        if (ret != OMPI_SUCCESS) {
-            return ret;
-        }
-    }
-
     if (module->flavor == MPI_WIN_FLAVOR_DYNAMIC) {
         ret = get_dynamic_win_info(remote_addr, module, target);
         if (ret != OMPI_SUCCESS) {
@@ -756,16 +774,43 @@ int ompi_osc_ucx_compare_and_swap(const void *origin_addr, const void *compare_a
         }
     }
 
-    uint64_t compare_val = opal_common_ucx_load_uint64(compare_addr, dt_bytes);
-    uint64_t value       = opal_common_ucx_load_uint64(origin_addr,  dt_bytes);
-    ret = opal_common_ucx_wpmem_cmpswp_nb(module->mem, compare_val, value, target,
-                                          result_addr, dt_bytes, remote_addr,
-                                          NULL, NULL);
+    ompi_datatype_type_size(dt, &dt_bytes);
+    if (4 == dt_bytes || 8 == dt_bytes) {
+        // fast path using UCX atomic operations
+        return do_atomic_compare_and_swap(origin_addr, compare_addr,
+                                          result_addr, dt, target,
+                                          remote_addr, module);
+    }
 
-    if (module->acc_single_intrinsic) {
+    /* fall back to get-compare-put */
+
+    ret = start_atomicity(module, target, &lock_acquired);
+    if (ret != OMPI_SUCCESS) {
         return ret;
     }
 
+    ret = opal_common_ucx_wpmem_putget(module->mem, OPAL_COMMON_UCX_GET, target,
+                                       &result_addr, dt_bytes, remote_addr);
+    if (OPAL_SUCCESS != ret) {
+        OSC_UCX_VERBOSE(1, "opal_common_ucx_mem_putget failed: %d", ret);
+        return OMPI_ERROR;
+    }
+
+    ret = opal_common_ucx_wpmem_flush(module->mem, OPAL_COMMON_UCX_SCOPE_EP, target);
+    if (ret != OPAL_SUCCESS) {
+        return ret;
+    }
+
+    if (0 == memcmp(result_addr, compare_addr, dt_bytes)) {
+        // write the new value
+        ret = opal_common_ucx_wpmem_putget(module->mem, OPAL_COMMON_UCX_PUT, target,
+                                           (void*)origin_addr, dt_bytes, remote_addr);
+        if (OPAL_SUCCESS != ret) {
+            OSC_UCX_VERBOSE(1, "opal_common_ucx_mem_putget failed: %d", ret);
+            return OMPI_ERROR;
+        }
+    }
+
     return end_atomicity(module, target, lock_acquired, NULL);
 }
 
diff --git a/opal/mca/common/ucx/common_ucx.h b/opal/mca/common/ucx/common_ucx.h
index f877742a2d..2baf6ea946 100644
--- a/opal/mca/common/ucx/common_ucx.h
+++ b/opal/mca/common/ucx/common_ucx.h
@@ -120,7 +120,7 @@ OPAL_DECLSPEC void opal_common_ucx_mca_var_register(const mca_base_component_t *
  * Load an integer value of \c size bytes from \c ptr and cast it to uint64_t.
  */
 static inline
-uint64_t opal_common_ucx_load_uint64(void *ptr, size_t size)
+uint64_t opal_common_ucx_load_uint64(const void *ptr, size_t size)
 {
     if (sizeof(uint8_t) == size) {
       return *(uint8_t*)ptr;