Port Compression: Making empty space reserved dynamic to 5.6

Summary:
* segment_reserve_factor determines the ratio of empty pages, the last
segment in an ibd can have before innodb creates a new extent. If a new
page is needed and the last segment has less than
    segment_reserve_factor * (current number of pages in this segment)
empty pages, then a new extent is created and the new page is allocated
from the new extent. The empty pages are useful when B-tree grows so
that pages in the upper level of the B-tree can be allocated
contiguously. An extent is 64 pages, and a segment is 256 extents.

Before this diff, this variable was not configurable and it was
determined by 1/x where x was the value defined by the compile time
than 1/8th pages were empty, then InnoDB would allocate a new extent
leaving many empty pages in the current extent. This caused lots of
fragmentation.

The ideal value for this variable needs investigation. The current
default will have the previous behavior. A segment has 16384 pages, so
for eg. If we are okay with leaving at most 16 empty pages per segment,
then we can set innodb_segment_reserve_factor=0.001.

innodb_segment_reserve_factor.test loads data into two identical tables
but sets a lower segment_reserve_factor before loading data to the
second table. This makes the second table about 10% smaller than the
first table.

The default value for this variable is set to 0.01 which should mean 1%
of the pages will be allocated for growth.

Test Plan: Tested on Jenkins.

Reviewers: nizamordulu, jtolmer

Reviewed By: tianx
(Original Reviewed By: nizamordulu)

mysql-test/suite/innodb_stress/r/innodb_segment_reserve_factor.result

@@ -0,0 +1,19 @@
+# create the actual table
+CREATE TABLE t1(
+id INT AUTO_INCREMENT PRIMARY KEY,
+msg VARCHAR(255),
+KEY msg_i(msg))
+ENGINE=INNODB
+ROW_FORMAT=COMPRESSED
+KEY_BLOCK_SIZE=8;
+# decompress the data file
+# t1 is populated with high segment_reserve_factor
+SET GLOBAL innodb_segment_reserve_factor = 0.125;
+LOAD DATA INFILE 'segment_reserve_factor.dat' INTO TABLE t1;
+# t2 is populated with low segment_reserve_factor
+SET GLOBAL innodb_segment_reserve_factor = 0.002;
+CREATE TABLE t2 like t1;
+LOAD DATA INFILE 'segment_reserve_factor.dat' INTO TABLE t2;
+# comparing the sizes of t1.ibd and t2.ibd (t2.ibd must be at most 95% of t1.ibd)
+'stat -c %s $MYSQLTEST_VARDIR/mysqld.1/data/test/t1.ibd  $MYSQLTEST_VARDIR/mysqld.1/data/test/t2.ibd | xargs | awk '{if ($2/$1 < .95) print "PASS"; else print "FAIL";}'
+PASS

mysql-test/suite/innodb_stress/t/innodb_segment_reserve_factor-master.opt

@@ -0,0 +1,2 @@
+--innodb-file-per-table
+--innodb-file-format=Barracuda

mysql-test/suite/innodb_stress/t/innodb_segment_reserve_factor.test

@@ -0,0 +1,42 @@
+--source include/have_innodb.inc
+--disable_query_log
+--disable_warnings
+DROP TABLE IF EXISTS t1, t2;
+--exec rm -f var/mysqld.1/data/test/segment_reserve_factor.dat
+--enable_warnings
+--let $segment_reserve_factor_save = `SELECT @@innodb_segment_reserve_factor`
+--enable_query_log
+
+--echo # create the actual table
+CREATE TABLE t1(
+  id INT AUTO_INCREMENT PRIMARY KEY,
+  msg VARCHAR(255),
+  KEY msg_i(msg))
+ENGINE=INNODB
+ROW_FORMAT=COMPRESSED
+KEY_BLOCK_SIZE=8;
+
+--echo # decompress the data file
+--exec gunzip -c suite/innodb_stress/t/innodb_segment_reserve_factor.dat.gz > $MYSQLTEST_VARDIR/mysqld.1/data/test/segment_reserve_factor.dat
+
+--echo # t1 is populated with high segment_reserve_factor
+SET GLOBAL innodb_segment_reserve_factor = 0.125;
+LOAD DATA INFILE 'segment_reserve_factor.dat' INTO TABLE t1;
+
+--echo # t2 is populated with low segment_reserve_factor
+SET GLOBAL innodb_segment_reserve_factor = 0.002;
+CREATE TABLE t2 like t1;
+LOAD DATA INFILE 'segment_reserve_factor.dat' INTO TABLE t2;
+
+--echo # comparing the sizes of t1.ibd and t2.ibd (t2.ibd must be at most 95% of t1.ibd)
+
+--let $cmd_string = 'stat -c %s \$MYSQLTEST_VARDIR/mysqld.1/data/test/t1.ibd  \$MYSQLTEST_VARDIR/mysqld.1/data/test/t2.ibd | xargs | awk '{if (\$2/\$1 < .95) print "PASS"; else print "FAIL";}'
+--let $cmd = stat -c %s $MYSQLTEST_VARDIR/mysqld.1/data/test/t1.ibd  $MYSQLTEST_VARDIR/mysqld.1/data/test/t2.ibd | xargs | awk '{if (\$2/\$1 < .95) print "PASS"; else print "FAIL";}'
+--echo $cmd_string
+--exec $cmd
+
+--disable_query_log
+DROP TABLE t1, t2;
+eval SET GLOBAL innodb_segment_reserve_factor=$segment_reserve_factor_save;
+--exec rm -f $MYSQL_VARDIR/mysqld.1/data/test/segment_reserve_factor.dat
+--enable_query_log

mysql-test/suite/sys_vars/r/innodb_segment_reserve_factor_basic.result

@@ -0,0 +1,18 @@
+SET @start_value = @@innodb_segment_reserve_factor;
+SELECT @start_value;
+@start_value
+0.01
+SET GLOBAL innodb_segment_reserve_factor = 0.0;
+Warnings:
+Warning	1292	Truncated incorrect innodb_segment_reserve_factor value: '0'
+SELECT @@innodb_segment_reserve_factor;
+@@innodb_segment_reserve_factor
+0.000300
+SET GLOBAL innodb_segment_reserve_factor = 0.1;
+SELECT @@innodb_segment_reserve_factor;
+@@innodb_segment_reserve_factor
+0.100000
+SET GLOBAL innodb_segment_reserve_factor = @start_value;
+SELECT @@innodb_segment_reserve_factor;
+@@innodb_segment_reserve_factor
+0.010000

mysql-test/suite/sys_vars/t/innodb_segment_reserve_factor_basic.test

@@ -0,0 +1,13 @@
+--source include/load_sysvars.inc
+
+
+SET @start_value = @@innodb_segment_reserve_factor;
+SELECT @start_value;
+
+SET GLOBAL innodb_segment_reserve_factor = 0.0;
+SELECT @@innodb_segment_reserve_factor;
+SET GLOBAL innodb_segment_reserve_factor = 0.1;
+SELECT @@innodb_segment_reserve_factor;
+
+SET GLOBAL innodb_segment_reserve_factor = @start_value;
+SELECT @@innodb_segment_reserve_factor;

storage/innobase/fsp/fsp0fsp.cc

@@ -50,6 +50,15 @@ Created 11/29/1995 Heikki Tuuri
 #include "dict0mem.h"
 #include "srv0start.h"
 
+double fseg_reserve_factor = 0.01; /* If this value is x, then if
+	        the number of unused but reserved
+	        pages in a segment is less than
+	        reserved pages * x, and there are
+	        at least FSEG_FRAG_LIMIT used pages,
+	        then we allow a new empty extent to
+	        be added to the segment in
+	        fseg_alloc_free_page. Otherwise, we
+	        use unused pages of the segment. */
 
 #ifndef UNIV_HOTBACKUP
 /** Flag to indicate if we have printed the tablespace full error. */
@@ -2384,7 +2393,7 @@ fseg_alloc_free_page_low(
 		goto got_hinted_page;
 		/*-----------------------------------------------------------*/
 	} else if (xdes_get_state(descr, mtr) == XDES_FREE
-		   && reserved - used < reserved / FSEG_FILLFACTOR
+		   && reserved - used < reserved * fseg_reserve_factor
 		   && used >= FSEG_FRAG_LIMIT) {
 
 		/* 2. We allocate the free extent from space and can take
@@ -2406,7 +2415,7 @@ fseg_alloc_free_page_low(
 		goto take_hinted_page;
 		/*-----------------------------------------------------------*/
 	} else if ((direction != FSP_NO_DIR)
-		   && ((reserved - used) < reserved / FSEG_FILLFACTOR)
+		   && ((reserved - used) < reserved * fseg_reserve_factor)
 		   && (used >= FSEG_FRAG_LIMIT)
 		   && (!!(ret_descr
 			  = fseg_alloc_free_extent(seg_inode,

storage/innobase/handler/ha_innodb.cc

@@ -16845,6 +16845,15 @@ static MYSQL_SYSVAR_BOOL(log_compressed_pages, page_zip_log_pages,
   " not deterministic.",
   NULL, innodb_log_compressed_pages_update, FALSE);
 
+static MYSQL_SYSVAR_DOUBLE(segment_reserve_factor, fseg_reserve_factor,
+  PLUGIN_VAR_OPCMDARG,
+  "If this value is x, then if the number of unused but reserved"
+  " pages in a segment is less than reserved pages * x, and there are"
+  " at least FSEG_FRAG_LIMIT used pages, then we allow a new empty extent to"
+  " be added to the segment in fseg_alloc_free_page. Otherwise, we"
+  " use unused pages of the segment.",
+  NULL, NULL, 0.01, 0.0003, 0.4, 0);
+
 static MYSQL_SYSVAR_LONG(additional_mem_pool_size, innobase_additional_mem_pool_size,
   PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_READONLY,
   "DEPRECATED. This option may be removed in future releases, "
@@ -17624,6 +17633,7 @@ static struct st_mysql_sys_var* innobase_system_variables[]= {
   MYSQL_SYSVAR(lra_pages_before_sleep),
   MYSQL_SYSVAR(lra_sleep),
   MYSQL_SYSVAR(lra_n_spaces),
+  MYSQL_SYSVAR(segment_reserve_factor),
   MYSQL_SYSVAR(zlib_wrap),
   MYSQL_SYSVAR(zlib_strategy),
   MYSQL_SYSVAR(lru_manager_max_sleep_time),

storage/innobase/include/fsp0fsp.h

@@ -36,6 +36,8 @@ Created 12/18/1995 Heikki Tuuri
 #include "page0types.h"
 #include "fsp0types.h"
 
+extern double fseg_reserve_factor;
+
 #endif /* !UNIV_INNOCHECKSUM */
 
 /* @defgroup fsp_flags InnoDB Tablespace Flag Constants @{ */
@@ -255,16 +257,6 @@ typedef	byte	fseg_inode_t;
 
 #define FSEG_MAGIC_N_VALUE	97937874
 
-#define	FSEG_FILLFACTOR		8	/* If this value is x, then if
-					the number of unused but reserved
-					pages in a segment is less than
-					reserved pages * 1/x, and there are
-					at least FSEG_FRAG_LIMIT used pages,
-					then we allow a new empty extent to
-					be added to the segment in
-					fseg_alloc_free_page. Otherwise, we
-					use unused pages of the segment. */
-
 #define FSEG_FRAG_LIMIT		FSEG_FRAG_ARR_N_SLOTS
 					/* If the segment has >= this many
 					used pages, it may be expanded by