stats: remove offsets on vpp side

Represent pointers directly in shared memory and require clients to adjust for
shared memory segment being mapped at different base address.
Deprecated: stat_segment_pointer() / stat_segment_offset()
Added: stat_segment_adjust()

Bumped the stat segment version to 2.

Type: refactor
Signed-off-by: Ole Troan <ot@cisco.com>
Change-Id: I33e756187b8903b45dcd353e6c1a101b7a4acb79

7 files changed, 82 insertions, 209 deletions

diff --git a/src/plugins/mactime/mactime_top.c b/src/plugins/mactime/mactime_top.c
index ee60535e0c2..473cc5b5c0e 100644
--- a/src/plugins/mactime/mactime_top.c
+++ b/src/plugins/mactime/mactime_top.c
@@ -1,7 +1,6 @@
 #include <vppinfra/time.h>
 #include <vppinfra/hash.h>
 #include <vppinfra/pool.h>
-#include <vpp/stats/stat_segment.h>
 #include <vpp-api/client/stat_client.h>
 #include <vppinfra/vec.h>
 #include <mactime/mactime_device.h>
@@ -11,9 +10,9 @@
 #include <vnet/api_errno.h>
 #include <svm/queue.h>
 
-/* define message IDs */
-#include <mactime/mactime.api_enum.h>
+#include <vnet/format_fns.h>
 #include <mactime/mactime.api_types.h>
+#include <mactime/mactime.api_enum.h>
 
 typedef struct
 {
@@ -108,14 +107,18 @@ vl_api_mactime_details_t_handler (vl_api_mactime_details_t * mp)
 }
 
 #define vl_print(handle, ...) fformat(handle, __VA_ARGS__)
+#define vl_endianfun		/* define message structures */
+#include <mactime/mactime.api.h>
+#undef vl_endianfun
 
-#define vl_endianfun
+/* instantiate all the print functions we know about */
 #define vl_printfun
+#include <mactime/mactime.api.h>
+#undef vl_printfun
+
 #define vl_api_version(n,v) static u32 api_version = v;
 #include <mactime/mactime.api.h>
 #undef vl_api_version
-#undef vl_printfun
-#undef vl_endianfun
 
 static int
 connect_to_vpp (char *name)
@@ -137,7 +140,7 @@ connect_to_vpp (char *name)
 
   vec_free (msg_base_lookup_name);
 
-  if (mm->msg_id_base == ~0)
+  if (mm->msg_id_base == (u16) ~ 0)
     return -1;
 
 #define _(N,n)                                                  \
@@ -183,7 +186,6 @@ scrape_stats_segment (mt_main_t * mm)
 {
   vlib_counter_t **counters_by_thread;
   vlib_counter_t *counters;
-  u64 *offset_vector;
   mactime_device_t *dev;
   stat_segment_access_t sa;
   stat_client_main_t *sm = mm->stat_client_main;
@@ -217,8 +219,7 @@ again1:
   stat_segment_access_start (&sa, sm);
 
   ep = vec_elt_at_index (sm->directory_vector, mm->ls_result1[0]);
-  counters_by_thread = stat_segment_pointer (sm->shared_header, ep->offset);
-  offset_vector = stat_segment_pointer (sm->shared_header, ep->offset_vector);
+  counters_by_thread = stat_segment_adjust (sm, ep->data);
 
   for (i = 0; i < vec_len (pool_indices); i++)
     {
@@ -230,8 +231,7 @@ again1:
 
       for (j = 0; j < vec_len (counters_by_thread); j++)
 	{
-	  counters = stat_segment_pointer (sm->shared_header,
-					   offset_vector[j]);
+	  counters = stat_segment_adjust (sm, counters_by_thread[j]);
 	  mm->allow_counters[index].packets += counters[index].packets;
 	  mm->allow_counters[index].bytes += counters[index].bytes;
 	}
@@ -252,8 +252,7 @@ again2:
   stat_segment_access_start (&sa, sm);
 
   ep = vec_elt_at_index (sm->directory_vector, mm->ls_result2[0]);
-  counters_by_thread = stat_segment_pointer (sm->shared_header, ep->offset);
-  offset_vector = stat_segment_pointer (sm->shared_header, ep->offset_vector);
+  counters_by_thread = stat_segment_adjust (sm, ep->data);
 
   for (i = 0; i < vec_len (pool_indices); i++)
     {
@@ -265,8 +264,7 @@ again2:
 
       for (j = 0; j < vec_len (counters_by_thread); j++)
 	{
-	  counters = stat_segment_pointer (sm->shared_header,
-					   offset_vector[j]);
+	  counters = stat_segment_adjust (sm, counters_by_thread[j]);
 	  mm->drop_counters[index].packets += counters[index].packets;
 	  mm->drop_counters[index].bytes += counters[index].bytes;
 	}
diff --git a/src/vpp-api/client/stat_client.c b/src/vpp-api/client/stat_client.c
index 54d6db660ee..56ff387d343 100644
--- a/src/vpp-api/client/stat_client.c
+++ b/src/vpp-api/client/stat_client.c
@@ -85,8 +85,8 @@ static stat_segment_directory_entry_t *
 get_stat_vector_r (stat_client_main_t * sm)
 {
   ASSERT (sm->shared_header);
-  return stat_segment_pointer (sm->shared_header,
-			       sm->shared_header->directory_offset);
+  return stat_segment_adjust (sm,
+			      (void *) sm->shared_header->directory_vector);
 }
 
 int
@@ -142,7 +142,7 @@ stat_segment_connect_r (const char *socket_name, stat_client_main_t * sm)
   sm->memory_size = st.st_size;
   sm->shared_header = memaddr;
   sm->directory_vector =
-    stat_segment_pointer (memaddr, sm->shared_header->directory_offset);
+    stat_segment_adjust (sm, (void *) sm->shared_header->directory_vector);
 
   return 0;
 }
@@ -199,7 +199,7 @@ copy_data (stat_segment_directory_entry_t * ep, stat_client_main_t * sm)
   int i;
   vlib_counter_t **combined_c;	/* Combined counter */
   counter_t **simple_c;		/* Simple counter */
-  uint64_t *offset_vector;
+  uint64_t *error_vector;
 
   assert (sm->shared_header);
 
@@ -212,67 +212,47 @@ copy_data (stat_segment_directory_entry_t * ep, stat_client_main_t * sm)
       break;
 
     case STAT_DIR_TYPE_COUNTER_VECTOR_SIMPLE:
-      if (ep->offset == 0)
-	return result;
-      simple_c = stat_segment_pointer (sm->shared_header, ep->offset);
+      simple_c = stat_segment_adjust (sm, ep->data);
       result.simple_counter_vec = vec_dup (simple_c);
-      offset_vector =
-	stat_segment_pointer (sm->shared_header, ep->offset_vector);
       for (i = 0; i < vec_len (simple_c); i++)
 	{
-	  counter_t *cb =
-	    stat_segment_pointer (sm->shared_header, offset_vector[i]);
+	  counter_t *cb = stat_segment_adjust (sm, simple_c[i]);
 	  result.simple_counter_vec[i] = vec_dup (cb);
 	}
       break;
 
     case STAT_DIR_TYPE_COUNTER_VECTOR_COMBINED:
-      if (ep->offset == 0)
-	return result;
-      combined_c = stat_segment_pointer (sm->shared_header, ep->offset);
+      combined_c = stat_segment_adjust (sm, ep->data);
       result.combined_counter_vec = vec_dup (combined_c);
-      offset_vector =
-	stat_segment_pointer (sm->shared_header, ep->offset_vector);
       for (i = 0; i < vec_len (combined_c); i++)
 	{
-	  vlib_counter_t *cb =
-	    stat_segment_pointer (sm->shared_header, offset_vector[i]);
+	  vlib_counter_t *cb = stat_segment_adjust (sm, combined_c[i]);
 	  result.combined_counter_vec[i] = vec_dup (cb);
 	}
       break;
 
     case STAT_DIR_TYPE_ERROR_INDEX:
       /* Gather errors from all threads into a vector */
-      offset_vector = stat_segment_pointer (sm->shared_header,
-					    sm->shared_header->error_offset);
-      vec_validate (result.error_vector, vec_len (offset_vector) - 1);
-      for (i = 0; i < vec_len (offset_vector); i++)
+      error_vector =
+	stat_segment_adjust (sm, (void *) sm->shared_header->error_vector);
+      vec_validate (result.error_vector, vec_len (error_vector) - 1);
+      for (i = 0; i < vec_len (error_vector); i++)
 	{
-	  counter_t *cb =
-	    stat_segment_pointer (sm->shared_header, offset_vector[i]);
+	  counter_t *cb = stat_segment_adjust (sm, (void *) error_vector[i]);
 	  result.error_vector[i] = cb[ep->index];
 	}
       break;
 
     case STAT_DIR_TYPE_NAME_VECTOR:
-      if (ep->offset == 0)
-	return result;
-      uint8_t **name_vector =
-	stat_segment_pointer (sm->shared_header, ep->offset);
-      result.name_vector = vec_dup (name_vector);
-      offset_vector =
-	stat_segment_pointer (sm->shared_header, ep->offset_vector);
-      for (i = 0; i < vec_len (name_vector); i++)
-	{
-	  if (offset_vector[i])
-	    {
-	      u8 *name =
-		stat_segment_pointer (sm->shared_header, offset_vector[i]);
-	      result.name_vector[i] = vec_dup (name);
-	    }
-	  else
-	    result.name_vector[i] = 0;
-	}
+      {
+	uint8_t **name_vector = stat_segment_adjust (sm, ep->data);
+	result.name_vector = vec_dup (name_vector);
+	for (i = 0; i < vec_len (name_vector); i++)
+	  {
+	    u8 *name = stat_segment_adjust (sm, name_vector[i]);
+	    result.name_vector[i] = vec_dup (name);
+	  }
+      }
       break;
 
     case STAT_DIR_TYPE_EMPTY:
diff --git a/src/vpp-api/client/stat_client.h b/src/vpp-api/client/stat_client.h
index 052d9692c88..9385cd242d5 100644
--- a/src/vpp-api/client/stat_client.h
+++ b/src/vpp-api/client/stat_client.h
@@ -101,6 +101,13 @@ _time_now_nsec (void)
   return 1e9 * ts.tv_sec + ts.tv_nsec;
 }
 
+static inline void *
+stat_segment_adjust (stat_client_main_t * sm, void *data)
+{
+  return (void *) ((char *) sm->shared_header +
+		   ((char *) data - (char *) sm->shared_header->base));
+}
+
 static inline int
 stat_segment_access_start (stat_segment_access_t * sa,
 			   stat_client_main_t * sm)
@@ -120,9 +127,10 @@ stat_segment_access_start (stat_segment_access_t * sa,
       while (shared_header->in_progress != 0)
 	;
     }
-  sm->directory_vector = (stat_segment_directory_entry_t *)
-    stat_segment_pointer (sm->shared_header,
-			  sm->shared_header->directory_offset);
+  sm->directory_vector =
+    (stat_segment_directory_entry_t *) stat_segment_adjust (sm,
+							    (void *)
+							    sm->shared_header->directory_vector);
   if (sm->timeout)
     return _time_now_nsec () < max_time ? 0 : -1;
   return 0;
@@ -147,7 +155,6 @@ stat_segment_access_end (stat_segment_access_t * sa, stat_client_main_t * sm)
   return true;
 }
 
-
 #endif /* included_stat_client_h */
 
 /*
diff --git a/src/vpp-api/python/vpp_papi/vpp_stats.py b/src/vpp-api/python/vpp_papi/vpp_stats.py
index aa3409554d0..1a65c8ebad8 100644
--- a/src/vpp-api/python/vpp_papi/vpp_stats.py
+++ b/src/vpp-api/python/vpp_papi/vpp_stats.py
@@ -25,11 +25,10 @@ typedef struct
 {
   stat_directory_type_t type;
   union {
-    uint64_t offset;
     uint64_t index;
     uint64_t value;
+    uint64_t *data;
   };
-  uint64_t offset_vector;
   char name[128]; // TODO change this to pointer to "somewhere"
 } stat_segment_directory_entry_t;
 
@@ -50,11 +49,11 @@ typedef struct
 typedef struct
 {
   uint64_t version;
+  void *base;
   uint64_t epoch;
   uint64_t in_progress;
-  uint64_t directory_offset;
-  uint64_t error_offset;
-  uint64_t stats_offset;
+  stat_segment_directory_entry_t *directory_vector;
+  uint64_t **error_vector;
 } stat_segment_shared_header_t;
 
 typedef struct
diff --git a/src/vpp/stats/stat_segment.c b/src/vpp/stats/stat_segment.c
index 8727122cee7..8255b16c010 100644
--- a/src/vpp/stats/stat_segment.c
+++ b/src/vpp/stats/stat_segment.c
@@ -157,7 +157,6 @@ vlib_stats_delete_cm (void *cm_arg)
   vlib_simple_counter_main_t *cm = (vlib_simple_counter_main_t *) cm_arg;
   stat_segment_main_t *sm = &stat_segment_main;
   stat_segment_directory_entry_t *e;
-  stat_segment_shared_header_t *shared_header = sm->shared_header;
 
   /* Not all counters have names / hash-table entries */
   if (!cm->name && !cm->stat_segment_name)
@@ -174,10 +173,7 @@ vlib_stats_delete_cm (void *cm_arg)
   e = &sm->directory_vector[index];
   hash_unset (sm->directory_vector_by_name, &e->name);
 
-  u64 *offset_vector = stat_segment_pointer (shared_header, e->offset_vector);
-
   void *oldheap = clib_mem_set_heap (sm->heap);	/* Enter stats segment */
-  vec_free (offset_vector);
   clib_mem_set_heap (oldheap);	/* Exit stats segment */
 
   memset (e, 0, sizeof (*e));
@@ -226,32 +222,10 @@ vlib_stats_pop_heap (void *cm_arg, void *oldheap, u32 cindex,
     }
 
   stat_segment_directory_entry_t *ep = &sm->directory_vector[vector_index];
-  ep->offset = stat_segment_offset (shared_header, cm->counters);	/* Vector of threads of vectors of counters */
-  u64 *offset_vector =
-    ep->offset_vector ? stat_segment_pointer (shared_header,
-					      ep->offset_vector) : 0;
-
-  /* Update the 2nd dimension offset vector */
-  int i;
-  vec_validate (offset_vector, vec_len (cm->counters) - 1);
-
-  if (sm->last != offset_vector)
-    {
-      for (i = 0; i < vec_len (cm->counters); i++)
-	offset_vector[i] =
-	  stat_segment_offset (shared_header, cm->counters[i]);
-    }
-  else
-    offset_vector[cindex] =
-      stat_segment_offset (shared_header, cm->counters[cindex]);
-
-  ep->offset_vector = stat_segment_offset (shared_header, offset_vector);
-  sm->directory_vector[vector_index].offset =
-    stat_segment_offset (shared_header, cm->counters);
+  ep->data = cm->counters;
 
   /* Reset the client hash table pointer, since it WILL change! */
-  shared_header->directory_offset =
-    stat_segment_offset (shared_header, sm->directory_vector);
+  shared_header->directory_vector = sm->directory_vector;
 
   vlib_stat_segment_unlock ();
   clib_mem_set_heap (oldheap);
@@ -278,13 +252,11 @@ vlib_stats_register_error_index (void *oldheap, u8 * name, u64 * em_vec,
       memcpy (e.name, name, vec_len (name));
       e.name[vec_len (name)] = '\0';
       e.type = STAT_DIR_TYPE_ERROR_INDEX;
-      e.offset = index;
-      e.offset_vector = 0;
+      e.index = index;
       vector_index = vlib_stats_create_counter (&e, oldheap);
 
       /* Warn clients to refresh any pointers they might be holding */
-      shared_header->directory_offset =
-	stat_segment_offset (shared_header, sm->directory_vector);
+      shared_header->directory_vector = sm->directory_vector;
     }
 
   vlib_stat_segment_unlock ();
@@ -293,45 +265,24 @@ vlib_stats_register_error_index (void *oldheap, u8 * name, u64 * em_vec,
 static void
 stat_validate_counter_vector (stat_segment_directory_entry_t * ep, u32 max)
 {
-  stat_segment_main_t *sm = &stat_segment_main;
-  stat_segment_shared_header_t *shared_header = sm->shared_header;
-  counter_t **counters =
-    ep->offset ? stat_segment_pointer (shared_header, ep->offset) : 0;
+  counter_t **counters = ep->data;
   vlib_thread_main_t *tm = vlib_get_thread_main ();
   int i;
-  u64 *offset_vector = 0;
 
   vec_validate_aligned (counters, tm->n_vlib_mains - 1,
 			CLIB_CACHE_LINE_BYTES);
-  ep->offset = stat_segment_offset (shared_header, counters);
-
   for (i = 0; i < tm->n_vlib_mains; i++)
-    {
-      vec_validate_aligned (counters[i], max, CLIB_CACHE_LINE_BYTES);
-      vec_add1 (offset_vector,
-		stat_segment_offset (shared_header, counters[i]));
-    }
+    vec_validate_aligned (counters[i], max, CLIB_CACHE_LINE_BYTES);
 
-  if (ep->offset_vector)
-    {
-      u64 *p = stat_segment_pointer (sm->shared_header, ep->offset_vector);
-      vec_free (p);
-    }
-  ep->offset_vector = stat_segment_offset (shared_header, offset_vector);
+  ep->data = counters;
 }
 
 always_inline void
 stat_set_simple_counter (stat_segment_directory_entry_t * ep,
 			 u32 thread_index, u32 index, u64 value)
 {
-  stat_segment_main_t *sm = &stat_segment_main;
-  stat_segment_shared_header_t *shared_header = sm->shared_header;
-
-  ASSERT (shared_header);
-  counter_t *offset_vector =
-    stat_segment_pointer (sm->shared_header, ep->offset_vector);
-  counter_t *cb =
-    stat_segment_pointer (sm->shared_header, offset_vector[thread_index]);
+  ASSERT (ep->data);
+  counter_t *cb = ep->data;
   cb[index] = value;
 }
 
@@ -349,13 +300,10 @@ vlib_stats_pop_heap2 (u64 * error_vector, u32 thread_index, void *oldheap,
 
   /* Reset the client hash table pointer, since it WILL change! */
   vec_validate (sm->error_vector, thread_index);
-  sm->error_vector[thread_index] =
-    stat_segment_offset (shared_header, error_vector);
+  sm->error_vector[thread_index] = error_vector;
 
-  shared_header->error_offset =
-    stat_segment_offset (shared_header, sm->error_vector);
-  shared_header->directory_offset =
-    stat_segment_offset (shared_header, sm->directory_vector);
+  shared_header->error_vector = sm->error_vector;
+  shared_header->directory_vector = sm->directory_vector;
 
   if (lock)
     vlib_stat_segment_unlock ();
@@ -402,6 +350,7 @@ vlib_map_stat_segment_init (void)
   sm->shared_header = shared_header = memaddr;
 
   shared_header->version = STAT_SEGMENT_VERSION;
+  shared_header->base = memaddr;
 
   sm->stat_segment_lockp = clib_mem_alloc (sizeof (clib_spinlock_t));
   clib_spinlock_init (sm->stat_segment_lockp);
@@ -420,9 +369,8 @@ vlib_map_stat_segment_init (void)
   sm->directory_vector[STAT_COUNTER_##E].type = STAT_DIR_TYPE_##t;
   foreach_stat_segment_counter_name
 #undef _
-    /* Save the vector offset in the shared segment, for clients */
-    shared_header->directory_offset =
-    stat_segment_offset (shared_header, sm->directory_vector);
+    /* Save the vector in the shared segment, for clients */
+    shared_header->directory_vector = sm->directory_vector;
 
   clib_mem_set_heap (oldheap);
 
@@ -482,7 +430,7 @@ format_stat_dir_entry (u8 * s, va_list * args)
       break;
     }
 
-  return format (s, format_string, ep->name, type_name, ep->offset);
+  return format (s, format_string, ep->name, type_name, 0);
 }
 
 static clib_error_t *
@@ -551,7 +499,6 @@ update_node_counters (stat_segment_main_t * sm)
   vlib_main_t **stat_vms = 0;
   vlib_node_t ***node_dups = 0;
   int i, j;
-  stat_segment_shared_header_t *shared_header = sm->shared_header;
   static u32 no_max_nodes = 0;
 
   vlib_node_get_nodes (0 /* vm, for barrier sync */ ,
@@ -582,16 +529,11 @@ update_node_counters (stat_segment_main_t * sm)
       vec_validate (sm->nodes, l - 1);
       stat_segment_directory_entry_t *ep;
       ep = &sm->directory_vector[STAT_COUNTER_NODE_NAMES];
-      ep->offset = stat_segment_offset (shared_header, sm->nodes);
+      ep->data = sm->nodes;
 
-      int i;
-      u64 *offset_vector =
-	ep->offset_vector ? stat_segment_pointer (shared_header,
-						  ep->offset_vector) : 0;
       /* Update names dictionary */
-      vec_validate (offset_vector, l - 1);
       vlib_node_t **nodes = node_dups[0];
-
+      int i;
       for (i = 0; i < vec_len (nodes); i++)
 	{
 	  vlib_node_t *n = nodes[i];
@@ -600,13 +542,7 @@ update_node_counters (stat_segment_main_t * sm)
 	  if (sm->nodes[n->index])
 	    vec_free (sm->nodes[n->index]);
 	  sm->nodes[n->index] = s;
-	  offset_vector[i] =
-	    sm->nodes[i] ? stat_segment_offset (shared_header,
-						sm->nodes[i]) : 0;
-
 	}
-      ep->offset_vector = stat_segment_offset (shared_header, offset_vector);
-
       vlib_stat_segment_unlock ();
       clib_mem_set_heap (oldheap);
       no_max_nodes = l;
@@ -622,31 +558,19 @@ update_node_counters (stat_segment_main_t * sm)
 	  counter_t *c;
 	  vlib_node_t *n = nodes[i];
 
-	  counters =
-	    stat_segment_pointer (shared_header,
-				  sm->directory_vector
-				  [STAT_COUNTER_NODE_CLOCKS].offset);
+	  counters = sm->directory_vector[STAT_COUNTER_NODE_CLOCKS].data;
 	  c = counters[j];
 	  c[n->index] = n->stats_total.clocks - n->stats_last_clear.clocks;
 
-	  counters =
-	    stat_segment_pointer (shared_header,
-				  sm->directory_vector
-				  [STAT_COUNTER_NODE_VECTORS].offset);
+	  counters = sm->directory_vector[STAT_COUNTER_NODE_VECTORS].data;
 	  c = counters[j];
 	  c[n->index] = n->stats_total.vectors - n->stats_last_clear.vectors;
 
-	  counters =
-	    stat_segment_pointer (shared_header,
-				  sm->directory_vector
-				  [STAT_COUNTER_NODE_CALLS].offset);
+	  counters = sm->directory_vector[STAT_COUNTER_NODE_CALLS].data;
 	  c = counters[j];
 	  c[n->index] = n->stats_total.calls - n->stats_last_clear.calls;
 
-	  counters =
-	    stat_segment_pointer (shared_header,
-				  sm->directory_vector
-				  [STAT_COUNTER_NODE_SUSPENDS].offset);
+	  counters = sm->directory_vector[STAT_COUNTER_NODE_SUSPENDS].data;
 	  c = counters[j];
 	  c[n->index] =
 	    n->stats_total.suspends - n->stats_last_clear.suspends;
@@ -879,8 +803,7 @@ stat_segment_register_gauge (u8 * name, stat_segment_update_fn update_fn,
   vlib_stat_segment_lock ();
   vector_index = vlib_stats_create_counter (&e, oldheap);
 
-  shared_header->directory_offset =
-    stat_segment_offset (shared_header, sm->directory_vector);
+  shared_header->directory_vector = sm->directory_vector;
 
   vlib_stat_segment_unlock ();
   clib_mem_set_heap (oldheap);
@@ -919,8 +842,7 @@ stat_segment_register_state_counter (u8 * name, u32 * index)
 
   vector_index = vlib_stats_create_counter (&e, oldheap);
 
-  shared_header->directory_offset =
-    stat_segment_offset (shared_header, sm->directory_vector);
+  shared_header->directory_vector = sm->directory_vector;
 
   vlib_stat_segment_unlock ();
   clib_mem_set_heap (oldheap);
@@ -1009,7 +931,6 @@ static clib_error_t *
 statseg_sw_interface_add_del (vnet_main_t * vnm, u32 sw_if_index, u32 is_add)
 {
   stat_segment_main_t *sm = &stat_segment_main;
-  stat_segment_shared_header_t *shared_header = sm->shared_header;
 
   void *oldheap = vlib_stats_push_heap (sm->interfaces);
   vlib_stat_segment_lock ();
@@ -1040,32 +961,7 @@ statseg_sw_interface_add_del (vnet_main_t * vnm, u32 sw_if_index, u32 is_add)
 
   stat_segment_directory_entry_t *ep;
   ep = &sm->directory_vector[STAT_COUNTER_INTERFACE_NAMES];
-  ep->offset = stat_segment_offset (shared_header, sm->interfaces);
-
-  int i;
-  u64 *offset_vector =
-    ep->offset_vector ? stat_segment_pointer (shared_header,
-					      ep->offset_vector) : 0;
-
-  vec_validate (offset_vector, vec_len (sm->interfaces) - 1);
-
-  if (sm->last != sm->interfaces)
-    {
-      /* the interface vector moved, so need to recalulate the offset array */
-      for (i = 0; i < vec_len (sm->interfaces); i++)
-	{
-	  offset_vector[i] =
-	    sm->interfaces[i] ? stat_segment_offset (shared_header,
-						     sm->interfaces[i]) : 0;
-	}
-    }
-  else
-    {
-      offset_vector[sw_if_index] =
-	sm->interfaces[sw_if_index] ?
-	stat_segment_offset (shared_header, sm->interfaces[sw_if_index]) : 0;
-    }
-  ep->offset_vector = stat_segment_offset (shared_header, offset_vector);
+  ep->data = sm->interfaces;
 
   vlib_stat_segment_unlock ();
   clib_mem_set_heap (oldheap);
diff --git a/src/vpp/stats/stat_segment.h b/src/vpp/stats/stat_segment.h
index 28e9ca3f778..a88067154f7 100644
--- a/src/vpp/stats/stat_segment.h
+++ b/src/vpp/stats/stat_segment.h
@@ -62,16 +62,10 @@ typedef enum
 #define STAT_SEGMENT_DEFAULT_SIZE	(32<<20)
 
 /* Shared segment memory layout version */
-#define STAT_SEGMENT_VERSION		1
+#define STAT_SEGMENT_VERSION		2
 
 #define STAT_SEGMENT_INDEX_INVALID	UINT32_MAX
 
-static inline uint64_t
-stat_segment_offset (void *start, void *data)
-{
-  return (char *) data - (char *) start;
-}
-
 typedef void (*stat_segment_update_fn)(stat_segment_directory_entry_t * e, u32 i);
 
 typedef struct {
@@ -88,7 +82,7 @@ typedef struct
   /* statistics segment */
   uword *directory_vector_by_name;
   stat_segment_directory_entry_t *directory_vector;
-  u64 *error_vector;
+  volatile u64 **error_vector;
   u8 **interfaces;
   u8 **nodes;
 
diff --git a/src/vpp/stats/stat_segment_shared.h b/src/vpp/stats/stat_segment_shared.h
index 982bddd66b6..b09e2b5618f 100644
--- a/src/vpp/stats/stat_segment_shared.h
+++ b/src/vpp/stats/stat_segment_shared.h
@@ -31,11 +31,10 @@ typedef struct
 {
   stat_directory_type_t type;
   union {
-    uint64_t offset;
     uint64_t index;
     uint64_t value;
+    void *data;
   };
-  uint64_t offset_vector;
   char name[128]; // TODO change this to pointer to "somewhere"
 } stat_segment_directory_entry_t;
 
@@ -45,11 +44,11 @@ typedef struct
 typedef struct
 {
   uint64_t version;
+  void *base;
   volatile uint64_t epoch;
   volatile uint64_t in_progress;
-  volatile uint64_t directory_offset;
-  volatile uint64_t error_offset;
-  volatile uint64_t stats_offset;
+  volatile stat_segment_directory_entry_t *directory_vector;
+  volatile uint64_t **error_vector;
 } stat_segment_shared_header_t;
 
 static inline void *