[RFC PATCH] plugins: expand the bb plugin to be thread safe and track per-cpu

[Alex Bennée]

While there isn't any easy way to make the inline counts thread safe
we can ensure the callback based ones are. While we are at it we can
reduce introduce a new option ("idle") to dump a report of the current
bb and insn count each time a vCPU enters the idle state.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: Dave Bort <dbort@dbort.com>
---
 tests/plugin/bb.c | 85 ++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 77 insertions(+), 8 deletions(-)

diff --git a/tests/plugin/bb.c b/tests/plugin/bb.c
index df19fd359df..5c08367d3d7 100644
--- a/tests/plugin/bb.c
+++ b/tests/plugin/bb.c
@@ -16,24 +16,68 @@
 
 QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
 
+/* Used by the inline counts */
 static uint64_t bb_count;
 static uint64_t insn_count;
 static bool do_inline;
 
+/* Dump running CPU total on idle? */
+static bool idle_report;
+
+typedef struct {
+    GMutex lock;
+    int index;
+    uint64_t bb_count;
+    uint64_t insn_count;
+} CPUCount;
+
+static GPtrArray *counts;
+static int max_cpus;
+
+static void gen_one_cpu_report(CPUCount *count, GString *report)
+{
+    if (count->bb_count) {
+        g_string_append_printf(report, "CPU%d: "
+                               "bb's: %" PRIu64", insns: %" PRIu64 "\n",
+                               count->index,
+                               count->bb_count, count->insn_count);
+    }
+}
+
 static void plugin_exit(qemu_plugin_id_t id, void *p)
 {
-    g_autofree gchar *out = g_strdup_printf(
-        "bb's: %" PRIu64", insns: %" PRIu64 "\n",
-        bb_count, insn_count);
-    qemu_plugin_outs(out);
+    g_autoptr(GString) report = g_string_new("");
+
+    if (do_inline) {
+        g_string_printf(report, "bb's: %" PRIu64", insns: %" PRIu64 "\n",
+                        bb_count, insn_count);
+    } else {
+        g_ptr_array_foreach(counts, (GFunc) gen_one_cpu_report, report);
+    }
+    qemu_plugin_outs(report->str);
+}
+
+static void vcpu_idle(qemu_plugin_id_t id, unsigned int cpu_index)
+{
+    CPUCount *count = g_ptr_array_index(counts, cpu_index);
+    g_autoptr(GString) report = g_string_new("");
+    gen_one_cpu_report(count, report);
+
+    if (report->len > 0) {
+        g_string_prepend(report, "Idling ");
+        qemu_plugin_outs(report->str);
+    }
 }
 
 static void vcpu_tb_exec(unsigned int cpu_index, void *udata)
 {
+    CPUCount *count = g_ptr_array_index(counts, cpu_index);
     unsigned long n_insns = (unsigned long)udata;
 
-    insn_count += n_insns;
-    bb_count++;
+    g_mutex_lock(&count->lock);
+    count->insn_count += n_insns;
+    count->bb_count++;
+    g_mutex_unlock(&count->lock);
 }
 
 static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
@@ -56,8 +100,33 @@ QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t 
id,
                                            const qemu_info_t *info,
                                            int argc, char **argv)
 {
-    if (argc && strcmp(argv[0], "inline") == 0) {
-        do_inline = true;
+    int i;
+
+    for (i = 0; i < argc; i++) {
+        char *opt = argv[i];
+        if (g_strcmp0(opt, "inline") == 0) {
+            do_inline = true;
+        } else if (g_strcmp0(opt, "idle") == 0) {
+            idle_report = true;
+        } else {
+            fprintf(stderr, "option parsing failed: %s\n", opt);
+            return -1;
+        }
+    }
+
+    if (!do_inline) {
+        max_cpus = info->system.max_vcpus;
+        counts = g_ptr_array_new();
+        for (i = 0; i < max_cpus; i++) {
+            CPUCount *count = g_new0(CPUCount, 1);
+            g_mutex_init(&count->lock);
+            count->index = i;
+            g_ptr_array_add(counts, count);
+        }
+    }
+
+    if (idle_report) {
+        qemu_plugin_register_vcpu_idle_cb(id, vcpu_idle);
     }
 
     qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans);
-- 
2.20.1