MYSQL-16: Augment mysqld_safe to flush caches and set numa policy.

Add a mysqld_safe option to flush (sync and drop) caches, specially
the page cache, before starting a mysqld server. This is useful for
establishing a consistent and predictable behavior for normal usage
and/or benchmarking.

Also, add an option to set an memory interleave policy. This causes
mysqld memory allocations to be interleaved in round-robing fashion
over the available nodes.

scripts/mysqld_safe.sh

@@ -17,6 +17,8 @@ MYSQLD=
 niceness=0
 mysqld_ld_preload=
 mysqld_ld_library_path=
+flush_caches=0
+numa_interleave=0
 
 # Initial logging status: error log is not open, and not using syslog
 logging=init
@@ -60,6 +62,9 @@ Usage: $0 [OPTIONS]
   --syslog                   Log messages to syslog with 'logger'
   --skip-syslog              Log messages to error log (default)
   --syslog-tag=TAG           Pass -t "mysqld-TAG" to 'logger'
+  --flush-caches             Flush and purge buffers/caches
+  --numa-interleave          Run mysqld with its memory interleaved
+                             on all CPUs
 
 All other options are passed to the mysqld program.
 
@@ -205,6 +210,8 @@ parse_arguments() {
       --skip-syslog) want_syslog=0 ;;
       --syslog-tag=*) syslog_tag="$val" ;;
       --timezone=*) TZ="$val"; export TZ; ;;
+      --flush-caches) flush_caches=1 ;;
+      --numa-interleave) numa_interleave=1 ;;
 
       --help) usage ;;
 
@@ -707,6 +714,41 @@ mysqld daemon not started"
   fi
 fi
 
+#
+# Flush and purge buffers/caches.
+#
+
+if @TARGET_LINUX@ && test $flush_caches -eq 1
+then
+  # Locate sync, ensure it exists.
+  if ! my_which sync > /dev/null 2>&1
+  then
+    log_error "sync command not found, required for --flush-caches"
+    exit 1
+  # Flush file system buffers.
+  elif ! sync
+  then
+    # Huh, the sync() function is always successful...
+    log_error "sync failed, check if sync is properly installed"
+  fi
+
+  # Locate sysctl, ensure it exists.
+  if ! my_which sysctl > /dev/null 2>&1
+  then
+    log_error "sysctl command not found, required for --flush-caches"
+    exit 1
+  # Purge page cache, dentries and inodes.
+  elif ! sysctl -q -w vm.drop_caches=3
+  then
+    log_error "sysctl failed, check the error message for details"
+    exit 1
+  fi
+elif test $flush_caches -eq 1
+then
+  log_error "--flush-caches is not supported on this platform"
+  exit 1
+fi
+
 #
 # Uncomment the following lines if you want all tables to be automatically
 # checked and repaired during startup. You should add sensible key_buffer
@@ -727,6 +769,31 @@ fi
 
 cmd="`mysqld_ld_preload_text`$NOHUP_NICENESS"
 
+#
+# Set mysqld's memory interleave policy.
+#
+
+if @TARGET_LINUX@ && test $numa_interleave -eq 1
+then
+  # Locate numactl, ensure it exists.
+  if ! my_which numactl > /dev/null 2>&1
+  then
+    log_error "numactl command not found, required for --numa-interleave"
+    exit 1
+  # Attempt to run a command, ensure it works.
+  elif ! numactl --interleave=all true
+  then
+    log_error "numactl failed, check if numactl is properly installed"
+  fi
+
+  # Launch mysqld with numactl.
+  cmd="$cmd numactl --interleave=all"
+elif test $numa_interleave -eq 1
+then
+  log_error "--numa-interleave is not supported on this platform"
+  exit 1
+fi
+
 for i in  "$ledir/$MYSQLD" "$defaults" "--basedir=$MY_BASEDIR_VERSION" \
   "--datadir=$DATADIR" "--plugin-dir=$plugin_dir" "$USER_OPTION"
 do