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[PATCH 02/10] repair: per AG locks contend for cachelines

To: xfs@xxxxxxxxxxx
Subject: [PATCH 02/10] repair: per AG locks contend for cachelines
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 27 Feb 2014 20:51:07 +1100
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1393494675-30194-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1393494675-30194-1-git-send-email-david@xxxxxxxxxxxxx>
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>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Brian Foster <bfoster@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 65281e4..afb26e0 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 (;;) {
                /*
@@ -925,7 +925,7 @@ 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 */
@@ -946,7 +946,7 @@ 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 4953a56..48f17ac 100644
--- a/repair/dinode.c
+++ b/repair/dinode.c
@@ -707,8 +707,8 @@ _("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;
                }
 
@@ -777,7 +777,7 @@ _("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 b12f48b..f1411a2 100644
--- a/repair/scan.c
+++ b/repair/scan.c
@@ -268,7 +268,7 @@ _("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:
@@ -314,7 +314,7 @@ _("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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