From 41c699dc128dbed9983810f6b9a1318beccbd35e Mon Sep 17 00:00:00 2001
From: Alexey Kopytov <akopytov@gmail.com>
Date: Sun, 27 May 2018 14:45:33 +0300
Subject: [PATCH] Bug #79455: Restore get_sched_indexer_t

This partially reverts the fix for bug bug#20709391 "SCHED_GETCPU() IN
DEFAULT GET_RND_INDEX() COULD NOT GENERATE RANDOM COUNTERS" by
re-introducing get_sched_indexer_t on Linux and Windows and using it (if
available) as the default indexer in ib_counter_t. It also changes
InnoDB row counter updates to use the default indexer rather than
override it with MySQL trx ID.

In sync_array_get() use the counter_indexer_t explicitly, because other
ones are not random enough per comments in the fix for bug #20709391.

This in itself does not introduce any measurable performance
improvements, but is rather a groundwork for further changes.
---
 storage/innobase/handler/ha_innodb.cc |  5 ++---
 storage/innobase/include/os0numa.h    |  2 +-
 storage/innobase/include/sync0arr.ic  |  2 +-
 storage/innobase/include/ut0counter.h | 28 ++++++++++++++++++++++++++++
 storage/innobase/row/row0mysql.cc     |  4 ++--
 5 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc
index fed9254f104..93ce5c7ac00 100644
--- a/storage/innobase/handler/ha_innodb.cc
+++ b/storage/innobase/handler/ha_innodb.cc
@@ -8645,8 +8645,7 @@ int ha_innobase::index_read(
   switch (ret) {
     case DB_SUCCESS:
       error = 0;
-      srv_stats.n_rows_read.add(thd_get_thread_id(m_prebuilt->trx->mysql_thd),
-                                1);
+      srv_stats.n_rows_read.inc();
       break;
 
     case DB_RECORD_NOT_FOUND:
@@ -8887,7 +8886,7 @@ int ha_innobase::general_fetch(
   switch (ret) {
     case DB_SUCCESS:
       error = 0;
-      srv_stats.n_rows_read.add(thd_get_thread_id(trx->mysql_thd), 1);
+      srv_stats.n_rows_read.inc();
       break;
     case DB_RECORD_NOT_FOUND:
       error = HA_ERR_END_OF_FILE;
diff --git a/storage/innobase/include/os0numa.h b/storage/innobase/include/os0numa.h
index 79e705c07b8..f64770675a3 100644
--- a/storage/innobase/include/os0numa.h
+++ b/storage/innobase/include/os0numa.h
@@ -48,7 +48,7 @@ this program; if not, write to the Free Software Foundation, Inc.,
 #endif /* HAVE_LIBNUMA */
 
 #ifdef HAVE_SCHED_GETCPU
-#include <utmpx.h>
+#include <sched.h>
 #endif /* HAVE_SCHED_GETCPU */
 
 #ifdef _WIN32
diff --git a/storage/innobase/include/sync0arr.ic b/storage/innobase/include/sync0arr.ic
index 4b5834e7f66..0f1ded1fd3e 100644
--- a/storage/innobase/include/sync0arr.ic
+++ b/storage/innobase/include/sync0arr.ic
@@ -47,7 +47,7 @@ sync_array_t *sync_array_get() {
   }
 
   return (
-      sync_wait_array[default_indexer_t<>::get_rnd_index() % sync_array_size]);
+      sync_wait_array[counter_indexer_t<>::get_rnd_index() % sync_array_size]);
 }
 
 /** Get an instance of the sync wait array and reserve a wait array cell
diff --git a/storage/innobase/include/ut0counter.h b/storage/innobase/include/ut0counter.h
index daeb1c16cc2..52fad0f040b 100644
--- a/storage/innobase/include/ut0counter.h
+++ b/storage/innobase/include/ut0counter.h
@@ -38,6 +38,7 @@ this program; if not, write to the Free Software Foundation, Inc.,
 
 #include "univ.i"
 
+#include "os0numa.h"
 #include "os0thread.h"
 #include "ut0dbg.h"
 
@@ -62,6 +63,29 @@ struct generic_indexer_t {
   }
 };
 
+#ifdef HAVE_OS_GETCPU
+/** Use the cpu id to index into the counter array. If it fails then
+use the thread id. */
+template <typename Type=ulint, int N=1>
+struct get_sched_indexer_t : public generic_indexer_t<Type, N> {
+  /** Default constructor/destructor should be OK. */
+
+  enum { fast = 1 };
+
+  /* @return result from sched_getcpu(), use thread id if it fails. */
+  static size_t get_rnd_index() UNIV_NOTHROW {
+
+    int cpu = os_getcpu();
+
+    if (unlikely(cpu < 0)) {
+      return static_cast<size_t>(os_thread_get_curr_id());
+    }
+
+    return(static_cast<size_t>(cpu));
+  }
+};
+#endif
+
 /** Use the result of my_timer_cycles(), which mainly uses RDTSC for cycles,
 to index into the counter array. See the comments for my_timer_cycles() */
 template <typename Type = ulint, int N = 1>
@@ -111,7 +135,11 @@ struct single_indexer_t {
   }
 };
 
+#ifdef HAVE_OS_GETCPU
+#define default_indexer_t get_sched_indexer_t
+#else
 #define default_indexer_t counter_indexer_t
+#endif
 
 /** Class for using fuzzy counters. The counter is not protected by any
 mutex and the results are not guaranteed to be 100% accurate but close
diff --git a/storage/innobase/row/row0mysql.cc b/storage/innobase/row/row0mysql.cc
index 2ca9a22c06f..2d03231c22c 100644
--- a/storage/innobase/row/row0mysql.cc
+++ b/storage/innobase/row/row0mysql.cc
@@ -2541,9 +2541,9 @@ dberr_t row_update_cascade_for_mysql(
     with a latch. */
     dict_table_n_rows_dec(table);
 
-    srv_stats.n_rows_deleted.add((size_t)trx->id, 1);
+    srv_stats.n_rows_deleted.inc();
   } else {
-    srv_stats.n_rows_updated.add((size_t)trx->id, 1);
+    srv_stats.n_rows_updated.inc();
   }
 
   row_update_statistics_if_needed(table);