perfmon: fix perf event user page read

[vpp.git] / src / plugins / perfmon / dispatch_wrapper.c

diff --git a/src/plugins/perfmon/dispatch_wrapper.c b/src/plugins/perfmon/dispatch_wrapper.c
index fe0a449..f5972f6 100644 (file)
--- a/src/plugins/perfmon/dispatch_wrapper.c
+++ b/src/plugins/perfmon/dispatch_wrapper.c
@@ -25,42 +25,64 @@
 
 #include <perfmon/perfmon.h>
 
+static_always_inline u64
+perfmon_mmap_read_pmc1 (const struct perf_event_mmap_page *mmap_page)
+{
+  u64 count;
+  u32 seq;
+
+  /* See documentation in /usr/include/linux/perf_event.h, for more details
+   * but the 2 main important things are:
+   *  1) if seq != mmap_page->lock, it means the kernel is currently updating
+   *     the user page and we need to read it again
+   *  2) if idx == 0, it means the perf event is currently turned off and we
+   *     just need to read the kernel-updated 'offset', otherwise we must also
+   *     add the current hw value (hence rdmpc) */
+  do
+    {
+      u32 idx;
+
+      seq = mmap_page->lock;
+      CLIB_COMPILER_BARRIER ();
+
+      idx = mmap_page->index;
+      count = mmap_page->offset;
+      if (idx)
+       count += _rdpmc (idx - 1);
+
+      CLIB_COMPILER_BARRIER ();
+    }
+  while (mmap_page->lock != seq);
+
+  return count;
+}
+
 static_always_inline void
-perfmon_read_pmcs (u64 *counters, int *pmc_index, u8 n_counters)
+perfmon_mmap_read_pmcs (u64 *counters,
+                       struct perf_event_mmap_page **mmap_pages,
+                       u8 n_counters)
 {
   switch (n_counters)
     {
     default:
     case 7:
-      counters[6] = _rdpmc (pmc_index[6]);
+      counters[6] = perfmon_mmap_read_pmc1 (mmap_pages[6]);
     case 6:
-      counters[5] = _rdpmc (pmc_index[5]);
+      counters[5] = perfmon_mmap_read_pmc1 (mmap_pages[5]);
     case 5:
-      counters[4] = _rdpmc (pmc_index[4]);
+      counters[4] = perfmon_mmap_read_pmc1 (mmap_pages[4]);
     case 4:
-      counters[3] = _rdpmc (pmc_index[3]);
+      counters[3] = perfmon_mmap_read_pmc1 (mmap_pages[3]);
     case 3:
-      counters[2] = _rdpmc (pmc_index[2]);
+      counters[2] = perfmon_mmap_read_pmc1 (mmap_pages[2]);
     case 2:
-      counters[1] = _rdpmc (pmc_index[1]);
+      counters[1] = perfmon_mmap_read_pmc1 (mmap_pages[1]);
     case 1:
-      counters[0] = _rdpmc (pmc_index[0]);
+      counters[0] = perfmon_mmap_read_pmc1 (mmap_pages[0]);
       break;
     }
 }
 
-static_always_inline int
-perfmon_calc_mmap_offset (perfmon_thread_runtime_t *tr, u8 i)
-{
-  return (int) (tr->mmap_pages[i]->index + tr->mmap_pages[i]->offset);
-}
-
-static_always_inline int
-perfmon_metric_index (perfmon_bundle_t *b, u8 i)
-{
-  return (int) (b->metrics[i]);
-}
-
 uword
 perfmon_dispatch_wrapper_mmap (vlib_main_t *vm, vlib_node_runtime_t *node,
                               vlib_frame_t *frame)
@@ -75,34 +97,13 @@ perfmon_dispatch_wrapper_mmap (vlib_main_t *vm, vlib_node_runtime_t *node,
 
   u64 before[PERF_MAX_EVENTS];
   u64 after[PERF_MAX_EVENTS];
-  int pmc_index[PERF_MAX_EVENTS];
   uword rv;
 
   clib_prefetch_load (s);
 
-  switch (n_events)
-    {
-    default:
-    case 7:
-      pmc_index[6] = perfmon_calc_mmap_offset (rt, 6);
-    case 6:
-      pmc_index[5] = perfmon_calc_mmap_offset (rt, 5);
-    case 5:
-      pmc_index[4] = perfmon_calc_mmap_offset (rt, 4);
-    case 4:
-      pmc_index[3] = perfmon_calc_mmap_offset (rt, 3);
-    case 3:
-      pmc_index[2] = perfmon_calc_mmap_offset (rt, 2);
-    case 2:
-      pmc_index[1] = perfmon_calc_mmap_offset (rt, 1);
-    case 1:
-      pmc_index[0] = perfmon_calc_mmap_offset (rt, 0);
-      break;
-    }
-
-  perfmon_read_pmcs (&before[0], pmc_index, n_events);
+  perfmon_mmap_read_pmcs (&before[0], rt->mmap_pages, n_events);
   rv = node->function (vm, node, frame);
-  perfmon_read_pmcs (&after[0], pmc_index, n_events);
+  perfmon_mmap_read_pmcs (&after[0], rt->mmap_pages, n_events);
 
   if (rv == 0)
     return rv;
@@ -116,6 +117,36 @@ perfmon_dispatch_wrapper_mmap (vlib_main_t *vm, vlib_node_runtime_t *node,
   return rv;
 }
 
+static_always_inline void
+perfmon_metric_read_pmcs (u64 *counters, int *pmc_index, u8 n_counters)
+{
+  switch (n_counters)
+    {
+    default:
+    case 7:
+      counters[6] = _rdpmc (pmc_index[6]);
+    case 6:
+      counters[5] = _rdpmc (pmc_index[5]);
+    case 5:
+      counters[4] = _rdpmc (pmc_index[4]);
+    case 4:
+      counters[3] = _rdpmc (pmc_index[3]);
+    case 3:
+      counters[2] = _rdpmc (pmc_index[2]);
+    case 2:
+      counters[1] = _rdpmc (pmc_index[1]);
+    case 1:
+      counters[0] = _rdpmc (pmc_index[0]);
+      break;
+    }
+}
+
+static_always_inline int
+perfmon_metric_index (perfmon_bundle_t *b, u8 i)
+{
+  return (int) (b->metrics[i]);
+}
+
 uword
 perfmon_dispatch_wrapper_metrics (vlib_main_t *vm, vlib_node_runtime_t *node,
                                  vlib_frame_t *frame)
@@ -154,11 +185,11 @@ perfmon_dispatch_wrapper_metrics (vlib_main_t *vm, vlib_node_runtime_t *node,
       break;
     }
 
-  perfmon_read_pmcs (&before[0], pmc_index, n_events);
+  perfmon_metric_read_pmcs (&before[0], pmc_index, n_events);
   rv = node->function (vm, node, frame);
 
   clib_memcpy_fast (&s->t[0].value[0], &before, sizeof (before));
-  perfmon_read_pmcs (&s->t[1].value[0], pmc_index, n_events);
+  perfmon_metric_read_pmcs (&s->t[1].value[0], pmc_index, n_events);
 
   if (rv == 0)
     return rv;