MDEV-17138 follow-up: Optimize fseg_create()

fseg_create(): Initialize FSEG_FRAG_ARRY by a single MLOG_MEMSET record.

flst_zero_addr(), flst_init(): Optimize away redundant writes.

fseg_free_page_low(): Write FIL_NULL by MLOG_MEMSET.

storage/innobase/fsp/fsp0fsp.cc

@@ -1881,7 +1881,6 @@ fseg_create(
 	buf_block_t*	block	= 0; /* remove warning */
 	fseg_header_t*	header	= 0; /* remove warning */
 	ulint		n_reserved;
-	ulint		i;
 
 	DBUG_ENTER("fseg_create");
 
@@ -1927,9 +1926,8 @@ fseg_create(
 	seg_id = mach_read_from_8(space_header + FSP_SEG_ID);
 
 	mlog_write_ull(space_header + FSP_SEG_ID, seg_id + 1, mtr);
-
 	mlog_write_ull(inode + FSEG_ID, seg_id, mtr);
-	mlog_write_ulint(inode + FSEG_NOT_FULL_N_USED, 0, MLOG_4BYTES, mtr);
+	ut_ad(!mach_read_from_4(inode + FSEG_NOT_FULL_N_USED));
 
 	flst_init(inode + FSEG_FREE, mtr);
 	flst_init(inode + FSEG_NOT_FULL, mtr);
@@ -1937,9 +1935,10 @@ fseg_create(
 
 	mlog_write_ulint(inode + FSEG_MAGIC_N, FSEG_MAGIC_N_VALUE,
 			 MLOG_4BYTES, mtr);
-	for (i = 0; i < FSEG_FRAG_ARR_N_SLOTS; i++) {
-		fseg_set_nth_frag_page_no(inode, i, FIL_NULL, mtr);
-	}
+	compile_time_assert(FSEG_FRAG_SLOT_SIZE == 4);
+	compile_time_assert(FIL_NULL == 0xffffffff);
+	mlog_memset(inode + FSEG_FRAG_ARR,
+		    FSEG_FRAG_SLOT_SIZE * FSEG_FRAG_ARR_N_SLOTS, 0xff, mtr);
 
 	if (page == 0) {
 		block = fseg_alloc_free_page_low(space,
@@ -2772,16 +2771,17 @@ fseg_free_page_low(
 
 	if (state != XDES_FSEG) {
 		/* The page is in the fragment pages of the segment */
-
 		for (ulint i = 0;; i++) {
 			if (fseg_get_nth_frag_page_no(seg_inode, i, mtr)
-			    == offset) {
+			    != offset) {
+				continue;
+			}
 
-				fseg_set_nth_frag_page_no(seg_inode, i,
-							  FIL_NULL, mtr);
+			compile_time_assert(FIL_NULL == 0xffffffff);
+			mlog_memset(seg_inode + FSEG_FRAG_ARR
+				    + i * FSEG_FRAG_SLOT_SIZE, 4, 0xff, mtr);
 			break;
 		}
-		}
 
 		fsp_free_page(space, offset, log, mtr);
 		return;

storage/innobase/include/fut0lst.h

@@ -85,8 +85,12 @@ inline void flst_init(buf_block_t* block, uint16_t ofs, mtr_t* mtr)
 @param[in,out]	mtr	mini-transaction */
 inline void flst_zero_addr(fil_faddr_t* faddr, mtr_t* mtr)
 {
+	if (mach_read_from_4(faddr + FIL_ADDR_PAGE) != FIL_NULL) {
 		mlog_memset(faddr + FIL_ADDR_PAGE, 4, 0xff, mtr);
+	}
+	if (mach_read_from_2(faddr + FIL_ADDR_BYTE)) {
 		mlog_write_ulint(faddr + FIL_ADDR_BYTE, 0, MLOG_2BYTES, mtr);
+	}
 }
 
 /********************************************************************//**

storage/innobase/include/fut0lst.ic

@@ -82,7 +82,9 @@ flst_init(
 					     MTR_MEMO_PAGE_X_FIX
 					     | MTR_MEMO_PAGE_SX_FIX));
 
+	if (mach_read_from_4(base + FLST_LEN)) {
 		mlog_write_ulint(base + FLST_LEN, 0, MLOG_4BYTES, mtr);
+	}
 	flst_zero_addr(base + FLST_FIRST, mtr);
 	flst_zero_addr(base + FLST_LAST, mtr);
 }