MDEV-33542 Inplace algorithm occupies more disk space compared to copy algorithm

Problem:
=======
- In case of large file size, InnoDB eagerly adds the new extent
even though there are many existing unused pages of the segment.
Reason is that in case of larger file size, threshold
(1/8 of reserved pages) for adding new extent has been
reached frequently.

Solution:
=========
- Try to utilise the unused pages in the segment before adding
the new extent in the file segment.

need_for_new_extent(): In case of larger file size, try to use
the 4 * FSP_EXTENT_SIZE as threshold to allocate the new extent.

fseg_alloc_free_page_low(): Rewrote the function to allocate
the page in the following order.
1) Try to get the page from existing segment extent.
2) Check whether the segment needs new extent
(need_for_new_extent()) and allocate the new extent,
find the page.
3) Take individual page from the unused page from
segment or tablespace.
4) Allocate a new extent and take first page from it.

Removed FSEG_FILLFACTOR, FSEG_FRAG_LIMIT variable.

mysql-test/suite/innodb/r/innodb_bug30113362.result

@@ -37,7 +37,7 @@ test.t1	analyze	status	Engine-independent statistics collected
 test.t1	analyze	status	OK
 SELECT CLUST_INDEX_SIZE FROM information_schema.INNODB_SYS_TABLESTATS WHERE NAME = 'test/t1';
 CLUST_INDEX_SIZE
-1856
+1792
 connection con2;
 DELETE FROM t1 WHERE a00 = 'cnm';
 COMMIT;
@@ -80,7 +80,7 @@ test.t1	analyze	status	Engine-independent statistics collected
 test.t1	analyze	status	OK
 SELECT CLUST_INDEX_SIZE FROM information_schema.INNODB_SYS_TABLESTATS WHERE NAME = 'test/t1';
 CLUST_INDEX_SIZE
-1856
+1792
 DELETE FROM t1 WHERE a00 = 'dpn';
 COMMIT;
 INSERT INTO t1 SET a00 = 'dpn';
@@ -117,6 +117,6 @@ test.t1	analyze	status	Engine-independent statistics collected
 test.t1	analyze	status	OK
 SELECT CLUST_INDEX_SIZE FROM information_schema.INNODB_SYS_TABLESTATS WHERE NAME = 'test/t1';
 CLUST_INDEX_SIZE
-1856
+1792
 SET DEBUG_SYNC = 'RESET';
 DROP TABLE t1;

storage/innobase/fsp/fsp0fsp.cc

@@ -271,7 +271,7 @@ inline void xdes_init(const buf_block_t &block, xdes_t *descr, mtr_t *mtr)
 static MY_ATTRIBUTE((nonnull, warn_unused_result))
 dberr_t
 fseg_mark_page_used(fseg_inode_t *seg_inode, buf_block_t *iblock,
-                    ulint page, xdes_t *descr, buf_block_t *xdes, mtr_t *mtr)
+                    uint32_t page, xdes_t *descr, buf_block_t *xdes, mtr_t *mtr)
 {
   ut_ad(fil_page_get_type(iblock->page.frame) == FIL_PAGE_INODE);
   ut_ad(!((page_offset(seg_inode) - FSEG_ARR_OFFSET) % FSEG_INODE_SIZE));
@@ -995,7 +995,7 @@ MY_ATTRIBUTE((nonnull, warn_unused_result))
 @return error code */
 static dberr_t
 fsp_alloc_from_free_frag(buf_block_t *header, buf_block_t *xdes, xdes_t *descr,
-			 ulint bit, mtr_t *mtr)
+			 uint32_t bit, mtr_t *mtr)
 {
   if (UNIV_UNLIKELY(xdes_get_state(descr) != XDES_FREE_FRAG ||
                     !xdes_is_free(descr, bit)))
@@ -1987,29 +1987,42 @@ fseg_alloc_free_page_low(
 		}
 	}
 
-	/* In the big if-else below we look for ret_page and ret_descr */
-	/*-------------------------------------------------------------*/
-	if ((xdes_get_state(descr) == XDES_FSEG)
-	    && mach_read_from_8(descr + XDES_ID) == seg_id
-	    && xdes_is_free(descr, hint % FSP_EXTENT_SIZE)) {
+	const uint32_t extent_size = FSP_EXTENT_SIZE;
+	ret_descr = descr;
+	/* Try to get the page from extent which belongs to segment */
+	if (xdes_get_state(descr) == XDES_FSEG
+	    && mach_read_from_8(descr + XDES_ID) == seg_id) {
+		/* Get the page from the segment extent */
+		if (xdes_is_free(descr, hint % extent_size)) {
 take_hinted_page:
-		/* 1. We can take the hinted page
-		=================================*/
-		ret_descr = descr;
-		ret_page = hint;
-		/* Skip the check for extending the tablespace. If the
-		page hint were not within the size of the tablespace,
-		we would have got (descr == NULL) above and reset the hint. */
-		goto got_hinted_page;
-		/*-----------------------------------------------------------*/
-	} else if (xdes_get_state(descr) == XDES_FREE
-		   && reserved - used < reserved / FSEG_FILLFACTOR
-		   && used >= FSEG_FRAG_LIMIT) {
-
-		/* 2. We allocate the free extent from space and can take
-		=========================================================
-		the hinted page
-		===============*/
+			ret_page = hint;
+			goto got_hinted_page;
+		} else if (!xdes_is_full(descr)) {
+			/* Take the page from the same extent as the
+			hinted page (and the extent already belongs to
+			the segment) */
+			ret_page = xdes_find_free(descr, hint % extent_size);
+			if (ret_page == FIL_NULL) {
+				ut_ad(!has_done_reservation);
+				return nullptr;
+			}
+			ret_page += xdes_get_offset(ret_descr);
+			goto alloc_done;
+		}
+	}
+
+	/** If the number of unused but reserved pages in a segment is
+	esser than minimum value of 1/8 of reserved pages or
+	4 * FSP_EXTENT_SIZE and there are at least half of extent size
+	used pages, then we allow a new empty extent to be added to
+	the segment in fseg_alloc_free_page_general(). Otherwise, we use
+	unused pages of the segment. */
+	if (used < extent_size / 2 ||
+            reserved - used >= reserved / 8 ||
+            reserved - used >= extent_size * 4) {
+	} else if (xdes_get_state(descr) == XDES_FREE) {
+		/* Allocate the free extent from space and can
+		take the hinted page */
 		ret_descr = fsp_alloc_free_extent(space, hint, &xdes,
 						  mtr, err);
 
@@ -2036,54 +2049,34 @@ fseg_alloc_free_page_low(
 
 		/* Try to fill the segment free list */
 		*err = fseg_fill_free_list(seg_inode, iblock, space,
-					   hint + FSP_EXTENT_SIZE, mtr);
+					   hint + extent_size, mtr);
 		if (UNIV_UNLIKELY(*err != DB_SUCCESS)) {
 			return nullptr;
 		}
 		goto take_hinted_page;
-		/*-----------------------------------------------------------*/
-	} else if ((direction != FSP_NO_DIR)
-		   && ((reserved - used) < reserved / FSEG_FILLFACTOR)
-		   && (used >= FSEG_FRAG_LIMIT)
-		   && (ret_descr = fseg_alloc_free_extent(seg_inode, iblock,
-							  &xdes, space,
-							  mtr, err))) {
-		/* 3. We take any free extent (which was already assigned above
-		===============================================================
-		in the if-condition to ret_descr) and take the lowest or
-		========================================================
-		highest page in it, depending on the direction
-		==============================================*/
+	} else if (direction != FSP_NO_DIR) {
+
+		ret_descr = fseg_alloc_free_extent(seg_inode, iblock,
+						   &xdes, space, mtr, err);
+
+		if (!ret_descr) {
+			ut_ad(*err != DB_SUCCESS);
+			return nullptr;
+		}
+		/* Take any free extent (which was already assigned
+		above in the if-condition to ret_descr) and take the
+		lowest or highest page in it, depending on the direction */
 		ret_page = xdes_get_offset(ret_descr);
 
 		if (direction == FSP_DOWN) {
-			ret_page += FSP_EXTENT_SIZE - 1;
+			ret_page += extent_size - 1;
 		}
-		ut_ad(!has_done_reservation || ret_page != FIL_NULL);
-		/*-----------------------------------------------------------*/
-	} else if (UNIV_UNLIKELY(*err != DB_SUCCESS)) {
-		return nullptr;
-	} else if ((xdes_get_state(descr) == XDES_FSEG)
-		   && mach_read_from_8(descr + XDES_ID) == seg_id
-		   && (!xdes_is_full(descr))) {
-
-		/* 4. We can take the page from the same extent as the
-		======================================================
-		hinted page (and the extent already belongs to the
-		==================================================
-		segment)
-		========*/
-		ret_descr = descr;
-		ret_page = xdes_find_free(ret_descr, hint % FSP_EXTENT_SIZE);
-		if (ret_page == FIL_NULL) {
-			ut_ad(!has_done_reservation);
-		} else {
-			ret_page += xdes_get_offset(ret_descr);
-		}
-		/*-----------------------------------------------------------*/
-	} else if (reserved - used > 0) {
-		/* 5. We take any unused page from the segment
-		==============================================*/
+		goto alloc_done;
+	}
+
+	/* Try to take individual page from the segment	or tablespace */
+	if (reserved - used > 0) {
+		/* Take any unused page from the segment */
 		fil_addr_t	first;
 
 		if (flst_get_len(seg_inode + FSEG_NOT_FULL) > 0) {
@@ -2092,7 +2085,7 @@ fseg_alloc_free_page_low(
 			first = flst_get_first(seg_inode + FSEG_FREE);
 		} else {
 			ut_ad(!has_done_reservation);
-			return(NULL);
+			return nullptr;
 		}
 
 		ret_descr = xdes_lst_get_descriptor(*space, first, mtr, &xdes);
@@ -2106,10 +2099,9 @@ fseg_alloc_free_page_low(
 		} else {
 			ret_page += xdes_get_offset(ret_descr);
 		}
-		/*-----------------------------------------------------------*/
-	} else if (used < FSEG_FRAG_LIMIT) {
-		/* 6. We allocate an individual page from the space
-		===================================================*/
+
+	} else if (used < extent_size / 2) {
+		/* Allocate an individual page from the space */
 		buf_block_t* block = fsp_alloc_free_page(
 			space, hint, mtr, init_mtr, err);
 
@@ -2132,13 +2124,11 @@ fseg_alloc_free_page_low(
 		/* fsp_alloc_free_page() invoked fsp_init_file_page()
 		already. */
 		return(block);
-		/*-----------------------------------------------------------*/
 	} else {
-		/* 7. We allocate a new extent and take its first page
-		======================================================*/
+		/* In worst case, try to allocate a new extent
+		and take its first page */
 		ret_descr = fseg_alloc_free_extent(seg_inode, iblock, &xdes,
 						   space, mtr, err);
-
 		if (!ret_descr) {
 			ut_ad(!has_done_reservation || *err);
 			return nullptr;
@@ -2151,14 +2141,13 @@ fseg_alloc_free_page_low(
 		/* Page could not be allocated */
 
 		ut_ad(!has_done_reservation);
-		return(NULL);
+		return nullptr;
 	}
-
+alloc_done:
 	if (space->size <= ret_page && !is_predefined_tablespace(space->id)) {
 		/* It must be that we are extending a single-table
 		tablespace whose size is still < 64 pages */
-
-		if (ret_page >= FSP_EXTENT_SIZE) {
+		if (ret_page >= extent_size) {
 			sql_print_error("InnoDB: Trying to extend '%s'"
 					" by single page(s) though the"
 					" space size " UINT32PF "."
@@ -2166,30 +2155,31 @@ fseg_alloc_free_page_low(
 					space->chain.start->name, space->size,
 					ret_page);
 			ut_ad(!has_done_reservation);
-			return(NULL);
+			return nullptr;
 		}
 
 		if (!fsp_try_extend_data_file_with_pages(
 			    space, ret_page, header, mtr)) {
 			/* No disk space left */
 			ut_ad(!has_done_reservation);
-			return(NULL);
+			return nullptr;
 		}
 	}
 
-got_hinted_page:
-	/* ret_descr == NULL if the block was allocated from free_frag
-	(XDES_FREE_FRAG) */
+	/* Skip the check for extending the tablespace.
+	If the page hint were not within the size of the tablespace,
+	descr set to nullptr above and reset the hint and the block
+	was allocated from free_frag (XDES_FREE_FRAG) */
 	if (ret_descr != NULL) {
+got_hinted_page:
 		/* At this point we know the extent and the page offset.
 		The extent is still in the appropriate list (FSEG_NOT_FULL
 		or FSEG_FREE), and the page is not yet marked as used. */
-
 		ut_d(buf_block_t* xxdes);
 		ut_ad(xdes_get_descriptor(space, ret_page, mtr, err, &xxdes)
 		      == ret_descr);
 		ut_ad(xdes == xxdes);
-		ut_ad(xdes_is_free(ret_descr, ret_page % FSP_EXTENT_SIZE));
+		ut_ad(xdes_is_free(ret_descr, ret_page % extent_size));
 
 		*err = fseg_mark_page_used(seg_inode, iblock, ret_page,
                                            ret_descr, xdes, mtr);

storage/innobase/include/fsp0fsp.h

@@ -209,24 +209,6 @@ typedef	byte	fseg_inode_t;
 
 static constexpr byte FSEG_MAGIC_N_BYTES[4]={0x05,0xd6,0x69,0xd2};
 
-#define	FSEG_FILLFACTOR		8	/* If the number of unused but reserved
-					pages in a segment is less than
-					reserved pages / FSEG_FILLFACTOR,
-					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_general().
-					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
-					allocating extents to the segment;
-					until that only individual fragment
-					pages are allocated from the space */
-
 #define	FSEG_FREE_LIST_LIMIT	40	/* If the reserved size of a segment
 					is at least this many extents, we
 					allow extents to be put to the free
@@ -294,7 +276,7 @@ Determine if a page is marked free.
 @param[in]	descr	extent descriptor
 @param[in]	offset	page offset within extent
 @return whether the page is free */
-inline bool xdes_is_free(const xdes_t *descr, ulint offset)
+inline bool xdes_is_free(const xdes_t *descr, uint32_t offset)
 {
   ut_ad(offset < FSP_EXTENT_SIZE);
   ulint index= XDES_FREE_BIT + XDES_BITS_PER_PAGE * offset;

storage/innobase/row/row0import.cc

@@ -610,7 +610,7 @@ class AbstractCallback
 
 		if (m_xdes != 0) {
 			const xdes_t*	xdesc = xdes(page_no, m_xdes);
-			ulint		pos = page_no % FSP_EXTENT_SIZE;
+			uint32_t	pos = page_no % FSP_EXTENT_SIZE;
 
 			return xdes_is_free(xdesc, pos);
 		}