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xfs: stagger the starting AG of scrub iscans to reduce contention
Online directory and parent repairs on parent-pointer equipped filesystems have shown that starting a large number of parallel iscans causes a lot of AGI buffer contention. Try to reduce this by making it so that iscans scan wrap around the end of the filesystem, and using a rotor to stagger where each scanner begins. Surprisingly, this boosts CPU utilization (on the author's test machines) from effectively single-threaded to 160%. Not great, but see the next patch. Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Darrick J. Wong
parent
4e98cc905c
commit
c473a3320b
@ -170,10 +170,24 @@ xchk_iscan_move_cursor(
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{
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struct xfs_scrub *sc = iscan->sc;
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struct xfs_mount *mp = sc->mp;
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xfs_ino_t cursor, visited;
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BUILD_BUG_ON(XFS_MAXINUMBER == NULLFSINO);
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/*
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* Special-case ino == 0 here so that we never set visited_ino to
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* NULLFSINO when wrapping around EOFS, for that will let through all
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* live updates.
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*/
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cursor = XFS_AGINO_TO_INO(mp, agno, agino);
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if (cursor == 0)
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visited = XFS_MAXINUMBER;
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else
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visited = cursor - 1;
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mutex_lock(&iscan->lock);
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iscan->cursor_ino = XFS_AGINO_TO_INO(mp, agno, agino);
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iscan->__visited_ino = iscan->cursor_ino - 1;
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iscan->cursor_ino = cursor;
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iscan->__visited_ino = visited;
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trace_xchk_iscan_move_cursor(iscan);
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mutex_unlock(&iscan->lock);
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}
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@ -257,12 +271,13 @@ xchk_iscan_advance(
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* Did not find any more inodes in this AG, move on to the next
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* AG.
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*/
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xchk_iscan_move_cursor(iscan, ++agno, 0);
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agno = (agno + 1) % mp->m_sb.sb_agcount;
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xchk_iscan_move_cursor(iscan, agno, 0);
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xfs_trans_brelse(sc->tp, agi_bp);
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xfs_perag_put(pag);
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trace_xchk_iscan_advance_ag(iscan);
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} while (agno < mp->m_sb.sb_agcount);
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} while (iscan->cursor_ino != iscan->scan_start_ino);
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xchk_iscan_finish(iscan);
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return 0;
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@ -420,6 +435,23 @@ xchk_iscan_teardown(
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mutex_destroy(&iscan->lock);
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}
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/* Pick an AG from which to start a scan. */
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static inline xfs_ino_t
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xchk_iscan_rotor(
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struct xfs_mount *mp)
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{
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static atomic_t agi_rotor;
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unsigned int r = atomic_inc_return(&agi_rotor) - 1;
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/*
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* Rotoring *backwards* through the AGs, so we add one here before
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* subtracting from the agcount to arrive at an AG number.
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*/
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r = (r % mp->m_sb.sb_agcount) + 1;
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return XFS_AGINO_TO_INO(mp, mp->m_sb.sb_agcount - r, 0);
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}
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/*
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* Set ourselves up to start an inode scan. If the @iget_timeout and
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* @iget_retry_delay parameters are set, the scan will try to iget each inode
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@ -434,15 +466,20 @@ xchk_iscan_start(
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unsigned int iget_retry_delay,
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struct xchk_iscan *iscan)
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{
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xfs_ino_t start_ino;
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start_ino = xchk_iscan_rotor(sc->mp);
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iscan->sc = sc;
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clear_bit(XCHK_ISCAN_OPSTATE_ABORTED, &iscan->__opstate);
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iscan->iget_timeout = iget_timeout;
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iscan->iget_retry_delay = iget_retry_delay;
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iscan->__visited_ino = 0;
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iscan->cursor_ino = 0;
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iscan->__visited_ino = start_ino;
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iscan->cursor_ino = start_ino;
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iscan->scan_start_ino = start_ino;
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mutex_init(&iscan->lock);
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trace_xchk_iscan_start(iscan);
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trace_xchk_iscan_start(iscan, start_ino);
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}
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/*
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@ -471,15 +508,45 @@ xchk_iscan_want_live_update(
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struct xchk_iscan *iscan,
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xfs_ino_t ino)
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{
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bool ret;
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bool ret = false;
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if (xchk_iscan_aborted(iscan))
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return false;
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mutex_lock(&iscan->lock);
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trace_xchk_iscan_want_live_update(iscan, ino);
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ret = iscan->__visited_ino >= ino;
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mutex_unlock(&iscan->lock);
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trace_xchk_iscan_want_live_update(iscan, ino);
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/* Scan is finished, caller should receive all updates. */
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if (iscan->__visited_ino == NULLFSINO) {
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ret = true;
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goto unlock;
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}
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/*
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* The visited cursor hasn't yet wrapped around the end of the FS. If
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* @ino is inside the starred range, the caller should receive updates:
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*
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* 0 ------------ S ************ V ------------ EOFS
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*/
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if (iscan->scan_start_ino <= iscan->__visited_ino) {
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if (ino >= iscan->scan_start_ino &&
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ino <= iscan->__visited_ino)
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ret = true;
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goto unlock;
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}
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/*
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* The visited cursor wrapped around the end of the FS. If @ino is
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* inside the starred range, the caller should receive updates:
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*
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* 0 ************ V ------------ S ************ EOFS
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*/
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if (ino >= iscan->scan_start_ino || ino <= iscan->__visited_ino)
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ret = true;
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unlock:
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mutex_unlock(&iscan->lock);
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return ret;
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}
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@ -12,6 +12,13 @@ struct xchk_iscan {
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/* Lock to protect the scan cursor. */
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struct mutex lock;
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/*
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* This is the first inode in the inumber address space that we
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* examined. When the scan wraps around back to here, the scan is
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* finished.
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*/
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xfs_ino_t scan_start_ino;
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/* This is the inode that will be examined next. */
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xfs_ino_t cursor_ino;
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@ -1173,25 +1173,27 @@ DEFINE_EVENT(xchk_iscan_class, name, \
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DEFINE_ISCAN_EVENT(xchk_iscan_move_cursor);
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DEFINE_ISCAN_EVENT(xchk_iscan_visit);
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DEFINE_ISCAN_EVENT(xchk_iscan_advance_ag);
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DEFINE_ISCAN_EVENT(xchk_iscan_start);
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DECLARE_EVENT_CLASS(xchk_iscan_ino_class,
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TP_PROTO(struct xchk_iscan *iscan, xfs_ino_t ino),
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TP_ARGS(iscan, ino),
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TP_STRUCT__entry(
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__field(dev_t, dev)
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__field(xfs_ino_t, startino)
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__field(xfs_ino_t, cursor)
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__field(xfs_ino_t, visited)
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__field(xfs_ino_t, ino)
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),
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TP_fast_assign(
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__entry->dev = iscan->sc->mp->m_super->s_dev;
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__entry->startino = iscan->scan_start_ino;
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__entry->cursor = iscan->cursor_ino;
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__entry->visited = iscan->__visited_ino;
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__entry->ino = ino;
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),
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TP_printk("dev %d:%d iscan cursor 0x%llx visited 0x%llx ino 0x%llx",
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TP_printk("dev %d:%d iscan start 0x%llx cursor 0x%llx visited 0x%llx ino 0x%llx",
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MAJOR(__entry->dev), MINOR(__entry->dev),
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__entry->startino,
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__entry->cursor,
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__entry->visited,
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__entry->ino)
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@ -1201,6 +1203,7 @@ DEFINE_EVENT(xchk_iscan_ino_class, name, \
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TP_PROTO(struct xchk_iscan *iscan, xfs_ino_t ino), \
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TP_ARGS(iscan, ino))
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DEFINE_ISCAN_INO_EVENT(xchk_iscan_want_live_update);
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DEFINE_ISCAN_INO_EVENT(xchk_iscan_start);
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TRACE_EVENT(xchk_iscan_iget,
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TP_PROTO(struct xchk_iscan *iscan, int error),
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