[PATCH 2/5] repair: per AG locks contend for cachelines

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From: Dave Chinner <dchinner@xxxxxxxxxx>

The per-ag locks used to protect per-ag block lists are located in a tightly
packed array. That means that they share cachelines, so separate them out inot
separate 64 byte regions in the array.

pahole confirms the padding is correctly applied:

struct aglock {
        pthread_mutex_t            lock;                 /*     0    40 */

        /* size: 64, cachelines: 1, members: 1 */
        /* padding: 24 */
};

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
 repair/dino_chunks.c | 24 ++++++++++++------------
 repair/dinode.c      |  6 +++---
 repair/globals.h     |  5 ++++-
 repair/incore.c      |  4 ++--
 repair/scan.c        |  4 ++--
 5 files changed, 23 insertions(+), 20 deletions(-)

diff --git a/repair/dino_chunks.c b/repair/dino_chunks.c
index d3c2236..02d32d8 100644
--- a/repair/dino_chunks.c
+++ b/repair/dino_chunks.c
@@ -141,7 +141,7 @@ verify_inode_chunk(xfs_mount_t		*mp,
 		if (check_aginode_block(mp, agno, agino) == 0)
 			return 0;
 
-		pthread_mutex_lock(&ag_locks[agno]);
+		pthread_mutex_lock(&ag_locks[agno].lock);
 
 		state = get_bmap(agno, agbno);
 		switch (state) {
@@ -166,7 +166,7 @@ verify_inode_chunk(xfs_mount_t		*mp,
 		_("inode block %d/%d multiply claimed, (state %d)\n"),
 				agno, agbno, state);
 			set_bmap(agno, agbno, XR_E_MULT);
-			pthread_mutex_unlock(&ag_locks[agno]);
+			pthread_mutex_unlock(&ag_locks[agno].lock);
 			return(0);
 		default:
 			do_warn(
@@ -176,7 +176,7 @@ verify_inode_chunk(xfs_mount_t		*mp,
 			break;
 		}
 
-		pthread_mutex_unlock(&ag_locks[agno]);
+		pthread_mutex_unlock(&ag_locks[agno].lock);
 
 		start_agino = XFS_OFFBNO_TO_AGINO(mp, agbno, 0);
 		*start_ino = XFS_AGINO_TO_INO(mp, agno, start_agino);
@@ -424,7 +424,7 @@ verify_inode_chunk(xfs_mount_t		*mp,
 	 * user data -- we're probably here as a result of a directory
 	 * entry or an iunlinked pointer
 	 */
-	pthread_mutex_lock(&ag_locks[agno]);
+	pthread_mutex_lock(&ag_locks[agno].lock);
 	for (cur_agbno = chunk_start_agbno;
 	     cur_agbno < chunk_stop_agbno;
 	     cur_agbno += blen)  {
@@ -438,7 +438,7 @@ verify_inode_chunk(xfs_mount_t		*mp,
 	_("inode block %d/%d multiply claimed, (state %d)\n"),
 				agno, cur_agbno, state);
 			set_bmap_ext(agno, cur_agbno, blen, XR_E_MULT);
-			pthread_mutex_unlock(&ag_locks[agno]);
+			pthread_mutex_unlock(&ag_locks[agno].lock);
 			return 0;
 		case XR_E_INO:
 			do_error(
@@ -449,7 +449,7 @@ verify_inode_chunk(xfs_mount_t		*mp,
 			break;
 		}
 	}
-	pthread_mutex_unlock(&ag_locks[agno]);
+	pthread_mutex_unlock(&ag_locks[agno].lock);
 
 	/*
 	 * ok, chunk is good.  put the record into the tree if required,
@@ -472,7 +472,7 @@ verify_inode_chunk(xfs_mount_t		*mp,
 
 	set_inode_used(irec_p, agino - start_agino);
 
-	pthread_mutex_lock(&ag_locks[agno]);
+	pthread_mutex_lock(&ag_locks[agno].lock);
 
 	for (cur_agbno = chunk_start_agbno;
 	     cur_agbno < chunk_stop_agbno;
@@ -505,7 +505,7 @@ verify_inode_chunk(xfs_mount_t		*mp,
 			break;
 		}
 	}
-	pthread_mutex_unlock(&ag_locks[agno]);
+	pthread_mutex_unlock(&ag_locks[agno].lock);
 
 	return(ino_cnt);
 }
@@ -736,7 +736,7 @@ process_inode_chunk(
 	/*
 	 * mark block as an inode block in the incore bitmap
 	 */
-	pthread_mutex_lock(&ag_locks[agno]);
+	pthread_mutex_lock(&ag_locks[agno].lock);
 	state = get_bmap(agno, agbno);
 	switch (state) {
 	case XR_E_INO:	/* already marked */
@@ -755,7 +755,7 @@ process_inode_chunk(
 			XFS_AGB_TO_FSB(mp, agno, agbno), state);
 		break;
 	}
-	pthread_mutex_unlock(&ag_locks[agno]);
+	pthread_mutex_unlock(&ag_locks[agno].lock);
 
 	for (;;) {
 		/*
@@ -914,7 +914,7 @@ process_inode_chunk(
 			ibuf_offset = 0;
 			agbno++;
 
-			pthread_mutex_lock(&ag_locks[agno]);
+			pthread_mutex_lock(&ag_locks[agno].lock);
 			state = get_bmap(agno, agbno);
 			switch (state) {
 			case XR_E_INO:	/* already marked */
@@ -935,7 +935,7 @@ process_inode_chunk(
 					XFS_AGB_TO_FSB(mp, agno, agbno), state);
 				break;
 			}
-			pthread_mutex_unlock(&ag_locks[agno]);
+			pthread_mutex_unlock(&ag_locks[agno].lock);
 
 		} else if (irec_offset == XFS_INODES_PER_CHUNK)  {
 			/*
diff --git a/repair/dinode.c b/repair/dinode.c
index 8f14a9e..77bbe40 100644
--- a/repair/dinode.c
+++ b/repair/dinode.c
@@ -700,8 +700,8 @@ _("Fatal error: inode %" PRIu64 " - blkmap_set_ext(): %s\n"
 		ebno = agbno + irec.br_blockcount;
 		if (agno != locked_agno) {
 			if (locked_agno != -1)
-				pthread_mutex_unlock(&ag_locks[locked_agno]);
-			pthread_mutex_lock(&ag_locks[agno]);
+				pthread_mutex_unlock(&ag_locks[locked_agno].lock);
+			pthread_mutex_lock(&ag_locks[agno].lock);
 			locked_agno = agno;
 		}
 
@@ -770,7 +770,7 @@ _("illegal state %d in block map %" PRIu64 "\n"),
 	error = 0;
 done:
 	if (locked_agno != -1)
-		pthread_mutex_unlock(&ag_locks[locked_agno]);
+		pthread_mutex_unlock(&ag_locks[locked_agno].lock);
 
 	if (i != *numrecs) {
 		ASSERT(i < *numrecs);
diff --git a/repair/globals.h b/repair/globals.h
index aef8b79..cbb2ce7 100644
--- a/repair/globals.h
+++ b/repair/globals.h
@@ -186,7 +186,10 @@ EXTERN xfs_extlen_t	sb_inoalignmt;
 EXTERN __uint32_t	sb_unit;
 EXTERN __uint32_t	sb_width;
 
-EXTERN pthread_mutex_t	*ag_locks;
+struct aglock {
+	pthread_mutex_t	lock __attribute__((__aligned__(64)));
+};
+EXTERN struct aglock	*ag_locks;
 
 EXTERN int 		report_interval;
 EXTERN __uint64_t 	*prog_rpt_done;
diff --git a/repair/incore.c b/repair/incore.c
index 3590464..a8d497e 100644
--- a/repair/incore.c
+++ b/repair/incore.c
@@ -294,13 +294,13 @@ init_bmaps(xfs_mount_t *mp)
 	if (!ag_bmap)
 		do_error(_("couldn't allocate block map btree roots\n"));
 
-	ag_locks = calloc(mp->m_sb.sb_agcount, sizeof(pthread_mutex_t));
+	ag_locks = calloc(mp->m_sb.sb_agcount, sizeof(struct aglock));
 	if (!ag_locks)
 		do_error(_("couldn't allocate block map locks\n"));
 
 	for (i = 0; i < mp->m_sb.sb_agcount; i++)  {
 		btree_init(&ag_bmap[i]);
-		pthread_mutex_init(&ag_locks[i], NULL);
+		pthread_mutex_init(&ag_locks[i].lock, NULL);
 	}
 
 	init_rt_bmap(mp);
diff --git a/repair/scan.c b/repair/scan.c
index 49ed194..f9afdb1 100644
--- a/repair/scan.c
+++ b/repair/scan.c
@@ -273,7 +273,7 @@ _("bad back (left) sibling pointer (saw %llu should be NULL (0))\n"
 		agno = XFS_FSB_TO_AGNO(mp, bno);
 		agbno = XFS_FSB_TO_AGBNO(mp, bno);
 
-		pthread_mutex_lock(&ag_locks[agno]);
+		pthread_mutex_lock(&ag_locks[agno].lock);
 		state = get_bmap(agno, agbno);
 		switch (state) {
 		case XR_E_UNKNOWN:
@@ -319,7 +319,7 @@ _("bad state %d, inode %" PRIu64 " bmap block 0x%" PRIx64 "\n"),
 				state, ino, bno);
 			break;
 		}
-		pthread_mutex_unlock(&ag_locks[agno]);
+		pthread_mutex_unlock(&ag_locks[agno].lock);
 	} else  {
 		/*
 		 * attribute fork for realtime files is in the regular
-- 
1.8.4.rc3

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