MINOR: cpu-topo: add new cpu-policies "group-by-2-clusters" and above

This adds "group-by-{2,3,4}-clusters", which, as its name implies,
create one thread group per X clusters. This can be useful when CPUs
are split into too small clusters, as well as when the total number
of assigned cores is not even between the clusters, to try to spread
the load between less different ones.

diff --git a/doc/configuration.txt b/doc/configuration.txt
index f9e96d6686222cb2da9772a6a9eb94435092a12d..868bdaeecf22ede48eeb7ae377fe2cbceed5b758 100644 (file)
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -1995,6 +1995,33 @@ cpu-policy <policy>
                         the limit of 32 or 64 depending on the system. This is
                         the default policy.
 
+   - group-by-2-clusters same as "group-by-cluster" but create a group every
+                        two clusters. This can make sense on CPUs having many
+                        clusters of few cores each, to avoid creating many
+                        groups, or to smooth the distribution a little bit when
+                        not all cores are in use. Please note that it can have
+                        very bad performance effects when the communication
+                        between clusters is slow. This is generally recommended
+                        against.
+
+   - group-by-3-clusters same as "group-by-cluster" but create a group every
+                        three clusters. This can make sense on CPUs having many
+                        clusters of few cores each, to avoid creating many
+                        groups, or to smooth the distribution a little bit when
+                        not all cores are in use. Please note that it can have
+                        very bad performance effects when the communication
+                        between clusters is slow. This is generally recommended
+                        against.
+
+   - group-by-4-clusters same as "group-by-cluster" but create a group every
+                        four clusters. This can make sense on CPUs having many
+                        clusters of few cores each, to avoid creating many
+                        groups, or to smooth the distribution a little bit when
+                        not all cores are in use. Please note that it can have
+                        very bad performance effects when the communication
+                        between clusters is slow. This is generally recommended
+                        against.
+
    - group-by-cluster   if neither "nbthread" not "nbtgroups" were set, then
                         one thread group is created for each CPU cluster with
                         available CPUs, each with as many threads as CPUs. All

diff --git a/src/cpu_topo.c b/src/cpu_topo.c
index 14bf93e81fbeb0966ff8c25f6d57ac69e616409a..0d3354a6c718d09424fa4480751572573f442800 100644 (file)
--- a/src/cpu_topo.c
+++ b/src/cpu_topo.c
@@ -61,6 +61,9 @@ static struct ha_cpu_policy ha_cpu_policy[] = {
        { .name = "none",               .desc = "use all available CPUs",                           .fct = NULL   },
        { .name = "first-usable-node",  .desc = "use only first usable node if nbthreads not set",  .fct = cpu_policy_first_usable_node, .arg = 0 },
        { .name = "group-by-cluster",   .desc = "make one thread group per core cluster",           .fct = cpu_policy_group_by_cluster , .arg = 1 },
+       { .name = "group-by-2-clusters",.desc = "make one thread group per 2 core clusters",        .fct = cpu_policy_group_by_cluster , .arg = 2 },
+       { .name = "group-by-3-clusters",.desc = "make one thread group per 3 core clusters",        .fct = cpu_policy_group_by_cluster , .arg = 3 },
+       { .name = "group-by-4-clusters",.desc = "make one thread group per 4 core clusters",        .fct = cpu_policy_group_by_cluster , .arg = 4 },
        { .name = "performance",        .desc = "make one thread group per perf. core cluster",     .fct = cpu_policy_performance      , .arg = 0 },
        { .name = "efficiency",         .desc = "make one thread group per eff. core cluster",      .fct = cpu_policy_efficiency       , .arg = 0 },
        { .name = "resource",           .desc = "make one thread group from the smallest cluster",  .fct = cpu_policy_resource         , .arg = 0 },
@@ -1063,6 +1066,8 @@ static int cpu_policy_first_usable_node(int policy, int tmin, int tmax, int gmin
  *  - otherwise tries to create one thread-group per cluster, with as many
  *    threads as CPUs in the cluster, and bind all the threads of this group
  *    to all the CPUs of the cluster.
+ * Also implements the variants "group-by-2-clusters", "group-by-3-clusters"
+ * and "group-by-4-clusters".
  */
 static int cpu_policy_group_by_cluster(int policy, int tmin, int tmax, int gmin, int gmax, char **err)
 {
@@ -1072,6 +1077,7 @@ static int cpu_policy_group_by_cluster(int policy, int tmin, int tmax, int gmin,
        int cid, lcid;
        int thr_per_grp, nb_grp;
        int thr;
+       int div;
 
        if (global.nbthread)
                return 0;
@@ -1082,6 +1088,11 @@ static int cpu_policy_group_by_cluster(int policy, int tmin, int tmax, int gmin,
        /* iterate over each new cluster */
        lcid = -1;
        cpu_start = 0;
+
+       /* used as a divisor of clusters*/
+       div = ha_cpu_policy[policy].arg;
+       div = div ? div : 1;
+
        while (global.nbtgroups < MAX_TGROUPS && global.nbthread < MAX_THREADS) {
                ha_cpuset_zero(&node_cpu_set);
                cid = -1; cpu_count = 0;
@@ -1090,14 +1101,14 @@ static int cpu_policy_group_by_cluster(int policy, int tmin, int tmax, int gmin,
                        /* skip disabled and already visited CPUs */
                        if (ha_cpu_topo[cpu].st & HA_CPU_F_EXCL_MASK)
                                continue;
-                       if (ha_cpu_topo[cpu].cl_gid <= lcid)
+                       if ((ha_cpu_topo[cpu].cl_gid / div) <= lcid)
                                continue;
 
                        if (cid < 0) {
-                               cid = ha_cpu_topo[cpu].cl_gid;
+                               cid = ha_cpu_topo[cpu].cl_gid / div;
                                cpu_start = cpu + 1;
                        }
-                       else if (cid != ha_cpu_topo[cpu].cl_gid)
+                       else if (cid != ha_cpu_topo[cpu].cl_gid / div)
                                continue;
 
                        /* make a mask of all of this cluster's CPUs */