[Xen-devel] [PATCH] xen: credit2: enable per cpu runqueue creation

[Praveen Kumar <kpraveen.lkml@xxxxxxxxx>]

The patch introduces a new command line option 'cpu' that when used will create
runqueue per logical pCPU. This may be useful for small systems, and also for
development, performance evalution and comparison.

Signed-off-by: Praveen Kumar <kpraveen.lkml@xxxxxxxxx>
Reviewed-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>

---
 docs/misc/xen-command-line.markdown |  3 ++-
 xen/common/sched_credit2.c          | 15 +++++++++++----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/docs/misc/xen-command-line.markdown 
b/docs/misc/xen-command-line.markdown
index 5815d87dab..6e73766574 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -525,7 +525,7 @@ also slow in responding to load changes.
 The default value of `1 sec` is rather long.
 
 ### credit2\_runqueue
-> `= core | socket | node | all`
+> `= cpu | core | socket | node | all`
 
 > Default: `socket`
 
@@ -536,6 +536,7 @@ balancing (for instance, it will deal better with 
hyperthreading),
 but also more overhead.
 
 Available alternatives, with their meaning, are:
+* `cpu`: one runqueue per each logical pCPUs of the host;
 * `core`: one runqueue per each physical core of the host;
 * `socket`: one runqueue per each physical socket (which often,
             but not always, matches a NUMA node) of the host;
diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
index bb1c657e76..ee7b443f9e 100644
--- a/xen/common/sched_credit2.c
+++ b/xen/common/sched_credit2.c
@@ -301,6 +301,9 @@ integer_param("credit2_balance_over", 
opt_overload_balance_tolerance);
  * want that to happen basing on topology. At the moment, it is possible
  * to choose to arrange runqueues to be:
  *
+ * - per-cpu: meaning that there will be one runqueue per logical cpu. This
+ *            will happen when if the opt_runqueue parameter is set to 'cpu'.
+ *
  * - per-core: meaning that there will be one runqueue per each physical
  *             core of the host. This will happen if the opt_runqueue
  *             parameter is set to 'core';
@@ -322,11 +325,13 @@ integer_param("credit2_balance_over", 
opt_overload_balance_tolerance);
  * either the same physical core, the same physical socket, the same NUMA
  * node, or just all of them, will be put together to form runqueues.
  */
-#define OPT_RUNQUEUE_CORE   0
-#define OPT_RUNQUEUE_SOCKET 1
-#define OPT_RUNQUEUE_NODE   2
-#define OPT_RUNQUEUE_ALL    3
+#define OPT_RUNQUEUE_CPU    0
+#define OPT_RUNQUEUE_CORE   1
+#define OPT_RUNQUEUE_SOCKET 2
+#define OPT_RUNQUEUE_NODE   3
+#define OPT_RUNQUEUE_ALL    4
 static const char *const opt_runqueue_str[] = {
+    [OPT_RUNQUEUE_CPU] = "cpu",
     [OPT_RUNQUEUE_CORE] = "core",
     [OPT_RUNQUEUE_SOCKET] = "socket",
     [OPT_RUNQUEUE_NODE] = "node",
@@ -682,6 +687,8 @@ cpu_to_runqueue(struct csched2_private *prv, unsigned int 
cpu)
         BUG_ON(cpu_to_socket(cpu) == XEN_INVALID_SOCKET_ID ||
                cpu_to_socket(peer_cpu) == XEN_INVALID_SOCKET_ID);
 
+        if (opt_runqueue == OPT_RUNQUEUE_CPU)
+            continue;
         if ( opt_runqueue == OPT_RUNQUEUE_ALL ||
              (opt_runqueue == OPT_RUNQUEUE_CORE && same_core(peer_cpu, cpu)) ||
              (opt_runqueue == OPT_RUNQUEUE_SOCKET && same_socket(peer_cpu, 
cpu)) ||
-- 
2.12.0


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