OSHMEM/COLL: optimization on zero-length ops

- removed barrier call on zero-length operations Signed-off-by: Sergey Oblomov <sergeyo@mellanox.com> (cherry picked from commit ff2fd0679eb4b31bfd840395d73746612e2670f4)
2018-11-26 10:41:33 +02:00 · 2018-11-26 10:41:33 +02:00 · 0a064d8c8d
--- a/oshmem/mca/scoll/basic/scoll_basic_alltoall.c
+++ b/oshmem/mca/scoll/basic/scoll_basic_alltoall.c
@ -61,17 +61,20 @@ int mca_scoll_basic_alltoall(struct oshmem_group_t *group,
        return OSHMEM_ERR_BAD_PARAM;
    }

-    if (nelems) {
-        if ((sst == 1) && (dst == 1)) {
-            rc = a2a_alg_simple(group, target, source, nelems, element_size);
-        } else {
-            rc = a2as_alg_simple(group, target, source, dst, sst, nelems,
-                                 element_size);
-        }
+    /* Do nothing on zero-length request */
+    if (OPAL_UNLIKELY(!nelems)) {
+        return OPAL_SUCCESS;
+    }

-        if (rc != OSHMEM_SUCCESS) {
-           return rc;
-        }
+    if ((sst == 1) && (dst == 1)) {
+        rc = a2a_alg_simple(group, target, source, nelems, element_size);
+    } else {
+        rc = a2as_alg_simple(group, target, source, dst, sst, nelems,
+                             element_size);
+    }
+
+    if (rc != OSHMEM_SUCCESS) {
+       return rc;
    }

    /* quiet is needed because scoll level barrier does not
--- a/oshmem/mca/scoll/basic/scoll_basic_broadcast.c
+++ b/oshmem/mca/scoll/basic/scoll_basic_broadcast.c
@ -55,6 +55,11 @@ int mca_scoll_basic_broadcast(struct oshmem_group_t *group,
    if ((rc == OSHMEM_SUCCESS) && oshmem_proc_group_is_member(group)) {
        int i = 0;

+        /* Do nothing on zero-length request */
+        if (OPAL_UNLIKELY(!nlong)) {
+            return OSHMEM_SUCCESS;
+        }
+
        if (pSync) {
            alg = (alg == SCOLL_DEFAULT_ALG ?
                    mca_scoll_basic_param_broadcast_algorithm : alg);
@ -131,7 +136,7 @@ static int _algorithm_central_counter(struct oshmem_group_t *group,
                  group->my_pe, pSync[0], PE_root);

    /* Check if this PE is the root */
-    if ((PE_root == group->my_pe) && nlong) {
+    if (PE_root == group->my_pe) {
        int pe_cur = 0;

        SCOLL_VERBOSE(14,
--- a/oshmem/mca/scoll/basic/scoll_basic_collect.c
+++ b/oshmem/mca/scoll/basic/scoll_basic_collect.c
@ -66,7 +66,12 @@ int mca_scoll_basic_collect(struct oshmem_group_t *group,
    if ((rc == OSHMEM_SUCCESS) && oshmem_proc_group_is_member(group)) {
        int i = 0;

-        if (nlong_type && nlong) {
+        /* Do nothing on zero-length request */
+        if (OPAL_UNLIKELY(!nlong)) {
+            return OPAL_SUCCESS;
+        }
+
+        if (nlong_type) {
            alg = (alg == SCOLL_DEFAULT_ALG ?
                    mca_scoll_basic_param_collect_algorithm : alg);
            switch (alg) {
@ -156,7 +161,7 @@ static int _algorithm_f_central_counter(struct oshmem_group_t *group,
                  group->my_pe);
    SCOLL_VERBOSE(15, "[#%d] pSync[0] = %ld", group->my_pe, pSync[0]);

-    if ((PE_root == group->my_pe) && nlong) {
+    if (PE_root == group->my_pe) {
        int pe_cur = 0;

        memcpy((void*) ((unsigned char*) target + 0 * nlong),
@ -543,7 +548,7 @@ static int _algorithm_central_collector(struct oshmem_group_t *group,
    /* Set own data size */
    pSync[0] = (nlong ? (long)nlong : SHMEM_SYNC_READY);

-    if ((PE_root == group->my_pe) && nlong) {
+    if (PE_root == group->my_pe) {
        long value = 0;
        int pe_cur = 0;
        long wait_pe_count = 0;
--- a/oshmem/mca/scoll/basic/scoll_basic_reduce.c
+++ b/oshmem/mca/scoll/basic/scoll_basic_reduce.c
@ -78,10 +78,14 @@ int mca_scoll_basic_reduce(struct oshmem_group_t *group,
    if ((rc == OSHMEM_SUCCESS) && oshmem_proc_group_is_member(group)) {
        int i = 0;

+        /* Do nothing on zero-length request */
+        if (OPAL_UNLIKELY(!nlong)) {
+            return OSHMEM_SUCCESS;
+        }
+
        if (pSync) {
-            alg = (nlong ? (alg == SCOLL_DEFAULT_ALG ?
-                                   mca_scoll_basic_param_reduce_algorithm : alg) :
-                           SCOLL_ALG_REDUCE_CENTRAL_COUNTER );
+            alg = (alg == SCOLL_DEFAULT_ALG ?
+                    mca_scoll_basic_param_reduce_algorithm : alg);
            switch (alg) {
            case SCOLL_ALG_REDUCE_CENTRAL_COUNTER:
                {
@ -186,7 +190,7 @@ static int _algorithm_central_counter(struct oshmem_group_t *group,

    SCOLL_VERBOSE(12, "[#%d] Reduce algorithm: Central Counter", group->my_pe);

-    if ((PE_root == group->my_pe) && nlong) {
+    if (PE_root == group->my_pe) {
        int pe_cur = 0;
        void *target_cur = NULL;

--- a/oshmem/mca/scoll/mpi/scoll_mpi_ops.c
+++ b/oshmem/mca/scoll/mpi/scoll_mpi_ops.c
@ -54,6 +54,12 @@ int mca_scoll_mpi_broadcast(struct oshmem_group_t *group,
    }
    dtype = &ompi_mpi_char.dt;
    root = oshmem_proc_group_find_id(group, PE_root);
+
+    /* Do nothing on zero-length request */
+    if (OPAL_UNLIKELY(!nlong)) {
+        return OSHMEM_SUCCESS;
+    }
+
    /* Open SHMEM specification has the following constrains (page 85):
     * "If using C/C++, nelems must be of type integer. If you are using Fortran, it must be a
     *  default integer value". And also fortran signature says "INTEGER".
@ -61,7 +67,7 @@ int mca_scoll_mpi_broadcast(struct oshmem_group_t *group,
     *  and considering this contradiction, we cast size_t to int here
     *  in case if the value is less than INT_MAX and fallback to previous module otherwise. */
 #ifdef INCOMPATIBLE_SHMEM_OMPI_COLL_APIS
-    if ((INT_MAX < nlong) || !nlong) {
+    if (INT_MAX < nlong) {
        MPI_COLL_VERBOSE(20,"RUNNING FALLBACK BCAST");
        PREVIOUS_SCOLL_FN(mpi_module, broadcast, group,
                PE_root,
@ -104,7 +110,13 @@ int mca_scoll_mpi_collect(struct oshmem_group_t *group,
    void *sbuf, *rbuf;
    MPI_COLL_VERBOSE(20,"RUNNING MPI ALLGATHER");
    mpi_module = (mca_scoll_mpi_module_t *) group->g_scoll.scoll_collect_module;
-    if ((nlong_type == true) && nlong) {
+
+    /* Do nothing on zero-length request */
+    if (OPAL_UNLIKELY(!nlong)) {
+        return OSHMEM_SUCCESS;
+    }
+
+    if (nlong_type == true) {
        sbuf = (void *) source;
        rbuf = target;
        stype =  &ompi_mpi_char.dt;
@ -177,6 +189,12 @@ int mca_scoll_mpi_reduce(struct oshmem_group_t *group,
    dtype = shmem_dtype_to_ompi_dtype(op);
    h_op = shmem_op_to_ompi_op(op->op);
    count = nlong/op->dt_size;
+
+    /* Do nothing on zero-length request */
+    if (OPAL_UNLIKELY(!nlong)) {
+        return OSHMEM_SUCCESS;
+    }
+
    /* Open SHMEM specification has the following constrains (page 85):
     * "If using C/C++, nelems must be of type integer. If you are using Fortran, it must be a
     *  default integer value". And also fortran signature says "INTEGER".
@ -184,7 +202,7 @@ int mca_scoll_mpi_reduce(struct oshmem_group_t *group,
     *  and considering this contradiction, we cast size_t to int here
     *  in case if the value is less than INT_MAX and fallback to previous module otherwise. */
 #ifdef INCOMPATIBLE_SHMEM_OMPI_COLL_APIS
-    if ((INT_MAX < count) || !nlong) {
+    if (INT_MAX < count) {
        MPI_COLL_VERBOSE(20,"RUNNING FALLBACK REDUCE");
        PREVIOUS_SCOLL_FN(mpi_module, reduce, group,
                op,