[Xen-devel] [RFC PATCH v1 4/8] xen: sched: Credit2: generalize topology related bootparam handling

[Dario Faggioli <dfaggioli@xxxxxxxx>]

Right now, runqueue organization is the only bit of the scheduler that
use such topology related information. But that may not be true forever,
i.e., there may be other boot parameters which takes the same "core",
"socket", etc, strings as argument.

In fact, this is the case of the credit2_group_sched parameter,
introduced in later patches.

Therefore, let's:
- make the #define-s more general, i.e., RUNQUEUE -> TOPOLOGY;
- do the parsing outside of the specific function handling the
  credit2_runqueue param.

While there, we also move "node" before "socket", so that we have them
ordered from the smallest to the largest, and we can do math with their
values. (Yes, I know, relationship between node and socket is not always
that clear, but, I've found boxes, like EPYC, with more than one node in
one socket, and I've never found one where two socket are in the same
node, so...)

No functional change intended.

Signed-off-by: Dario Faggioli <dfaggioli@xxxxxxxx>
---
Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
---
 xen/common/sched_credit2.c |   61 +++++++++++++++++++++++++-------------------
 1 file changed, 35 insertions(+), 26 deletions(-)

diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
index 617a7ece6e..9550503b5b 100644
--- a/xen/common/sched_credit2.c
+++ b/xen/common/sched_credit2.c
@@ -434,34 +434,43 @@ integer_param("credit2_cap_period_ms", opt_cap_period);
  * 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_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",
-    [OPT_RUNQUEUE_ALL] = "all"
+#define OPT_TOPOLOGY_CPU    0
+#define OPT_TOPOLOGY_CORE   1
+#define OPT_TOPOLOGY_NODE   2
+#define OPT_TOPOLOGY_SOCKET 3
+#define OPT_TOPOLOGY_ALL    4
+static const char *const opt_topospan_str[] = {
+    [OPT_TOPOLOGY_CPU] = "cpu",
+    [OPT_TOPOLOGY_CORE] = "core",
+    [OPT_TOPOLOGY_NODE] = "node",
+    [OPT_TOPOLOGY_SOCKET] = "socket",
+    [OPT_TOPOLOGY_ALL] = "all"
 };
-static int __read_mostly opt_runqueue = OPT_RUNQUEUE_SOCKET;
 
-static int __init parse_credit2_runqueue(const char *s)
+static int __init parse_topology_span(const char *s)
 {
     unsigned int i;
 
-    for ( i = 0; i < ARRAY_SIZE(opt_runqueue_str); i++ )
+    for ( i = 0; i < ARRAY_SIZE(opt_topospan_str); i++ )
     {
-        if ( !strcmp(s, opt_runqueue_str[i]) )
-        {
-            opt_runqueue = i;
-            return 0;
-        }
+        if ( !strcmp(s, opt_topospan_str[i]) )
+            return i;
     }
 
-    return -EINVAL;
+    return -1;
+}
+
+static int __read_mostly opt_runqueue = OPT_TOPOLOGY_SOCKET;
+
+static int __init parse_credit2_runqueue(const char *s)
+{
+    opt_runqueue = parse_topology_span(s);
+
+    if ( opt_runqueue < 0 )
+        return -EINVAL;
+
+    ASSERT(opt_runqueue <= OPT_TOPOLOGY_ALL );
+    return 0;
 }
 custom_param("credit2_runqueue", parse_credit2_runqueue);
 
@@ -883,12 +892,12 @@ 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)
+        if (opt_runqueue == OPT_TOPOLOGY_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)) ||
-             (opt_runqueue == OPT_RUNQUEUE_NODE && same_node(peer_cpu, cpu)) )
+        if ( opt_runqueue == OPT_TOPOLOGY_ALL ||
+             (opt_runqueue == OPT_TOPOLOGY_CORE && same_core(peer_cpu, cpu)) ||
+             (opt_runqueue == OPT_TOPOLOGY_SOCKET && same_socket(peer_cpu, 
cpu)) ||
+             (opt_runqueue == OPT_TOPOLOGY_NODE && same_node(peer_cpu, cpu)) )
             break;
     }
 
@@ -4021,7 +4030,7 @@ csched2_init(struct scheduler *ops)
            opt_load_window_shift,
            opt_underload_balance_tolerance,
            opt_overload_balance_tolerance,
-           opt_runqueue_str[opt_runqueue],
+           opt_topospan_str[opt_runqueue],
            opt_cap_period);
 
     printk(XENLOG_INFO "load tracking window length %llu ns\n",


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