Replace the default indexer for ib_counter_t values for performance

Summary: The default indexer for ib_counter_t values uses the result from 'pthread_self() % 64' to index into an array.  Since pthread_self() likely returns a pointer to an internal structure on 64-bit platforms 'pthread_self() % 64' will often (always?) result in 0.  This diff switches to using a different indexer that uses the current CPU when the sched_getcpu() function is available.

Test Plan: MTR

Reviewers: yoshinorim, MarkCallaghan

Reviewed By: MarkCallaghan

Subscribers: webscalesql-eng

Differential Revision: https://reviews.facebook.net/D65427

include/ut0counter.h

@@ -55,7 +55,8 @@ struct generic_indexer_t {
 };
 
 #ifdef HAVE_SCHED_GETCPU
-#include <utmpx.h>
+//#include <utmpx.h>  // Including this causes problems with EMPTY symbol
+#include <sched.h>  // Include this instead
 /** Use the cpu id to index into the counter array. If it fails then
 use the thread id. */
 template <typename Type, int N>
@@ -66,7 +67,7 @@ struct get_sched_indexer_t : public generic_indexer_t<Type, N> {
 	size_t get_rnd_index() const {
 
 		size_t	cpu = sched_getcpu();
-		if (cpu == -1) {
+		if (cpu == (size_t) -1) {
 			cpu = get_curr_thread_id();
 		}
 

storage/rocksdb/CMakeLists.txt

@@ -4,6 +4,11 @@ IF (NOT EXISTS "${CMAKE_SOURCE_DIR}/rocksdb/Makefile")
   MESSAGE(SEND_ERROR "Missing Makefile in rocksdb directory. Try \"git submodule update\".")
 ENDIF()
 
+CHECK_FUNCTION_EXISTS(sched_getcpu  HAVE_SCHED_GETCPU)
+IF(HAVE_SCHED_GETCPU)
+  ADD_DEFINITIONS(-DHAVE_SCHED_GETCPU=1)
+ENDIF()
+
 # get a list of rocksdb library source files
 # run with env -i to avoid passing variables
 EXECUTE_PROCESS(

storage/rocksdb/ha_rocksdb.cc

@@ -3641,6 +3641,18 @@ static int rocksdb_init_func(void *p)
     rdb->PauseBackgroundWork();
   }
 
+  // NO_LINT_DEBUG
+  sql_print_information("RocksDB: global statistics using %s indexer",
+      STRINGIFY_ARG(RDB_INDEXER));
+#if defined(HAVE_SCHED_GETCPU)
+  if (sched_getcpu() == -1)
+  {
+    // NO_LINT_DEBUG
+    sql_print_information("RocksDB: sched_getcpu() failed - "
+        "global statistics will use thread_id_indexer_t instead");
+  }
+#endif
+
   sql_print_information("RocksDB instance opened");
   DBUG_RETURN(0);
 }

storage/rocksdb/ha_rocksdb.h

@@ -237,13 +237,19 @@ enum operation_type {
   ROWS_MAX
 };
 
+#if defined(HAVE_SCHED_GETCPU)
+#define RDB_INDEXER get_sched_indexer_t
+#else
+#define RDB_INDEXER thread_id_indexer_t
+#endif
+
 /* Global statistics struct used inside MyRocks */
 struct st_global_stats {
-  ib_counter_t<ulonglong, 64> rows[ROWS_MAX];
+  ib_counter_t<ulonglong, 64, RDB_INDEXER> rows[ROWS_MAX];
 
   // system_rows_ stats are only for system
   // tables. They are not counted in rows_* stats.
-  ib_counter_t<ulonglong, 64> system_rows[ROWS_MAX];
+  ib_counter_t<ulonglong, 64, RDB_INDEXER> system_rows[ROWS_MAX];
 };
 
 /* Struct used for exporting status to MySQL */