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From: Dave Chinner <david@fromorbit.com>
To: xfs@oss.sgi.com
Subject: [PATCH 06/14] xfs: convert l_last_sync_lsn to an atomic variable
Date: Mon, 29 Nov 2010 12:38:24 +1100	[thread overview]
Message-ID: <1290994712-21376-7-git-send-email-david@fromorbit.com> (raw)
In-Reply-To: <1290994712-21376-1-git-send-email-david@fromorbit.com>

From: Dave Chinner <dchinner@redhat.com>

log->l_last_sync_lsn is updated in only one critical spot - log
buffer Io completion - and is protected by the grant lock here. This
requires the grant lock to be taken for every log buffer IO
completion. Converting the l_last_sync_lsn variable to an atomic64_t
means that we do not need to take the grant lock in log buffer IO
completion to update it.

This also removes the need for explicitly holding a spinlock to read
the l_last_sync_lsn on 32 bit platforms.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/xfs_log.c         |   57 ++++++++++++++++++++-------------------------
 fs/xfs/xfs_log_priv.h    |    9 ++++++-
 fs/xfs/xfs_log_recover.c |    6 ++--
 3 files changed, 36 insertions(+), 36 deletions(-)

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index a35ef8f..90a605cc 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -360,7 +360,7 @@ xfs_log_reserve(
 
 		spin_lock(&log->l_grant_lock);
 		xlog_grant_push_ail(log, log->l_tail_lsn,
-				    log->l_last_sync_lsn,
+				    atomic64_read(&log->l_last_sync_lsn),
 				    internal_ticket->t_unit_res);
 		spin_unlock(&log->l_grant_lock);
 		retval = xlog_regrant_write_log_space(log, internal_ticket);
@@ -378,7 +378,7 @@ xfs_log_reserve(
 
 		spin_lock(&log->l_grant_lock);
 		xlog_grant_push_ail(log, log->l_tail_lsn,
-				    log->l_last_sync_lsn,
+				    atomic64_read(&log->l_last_sync_lsn),
 				    (internal_ticket->t_unit_res *
 				     internal_ticket->t_cnt));
 		spin_unlock(&log->l_grant_lock);
@@ -718,12 +718,8 @@ xfs_log_move_tail(xfs_mount_t	*mp,
 	if (XLOG_FORCED_SHUTDOWN(log))
 		return;
 
-	if (tail_lsn == 0) {
-		/* needed since sync_lsn is 64 bits */
-		spin_lock(&log->l_icloglock);
-		tail_lsn = log->l_last_sync_lsn;
-		spin_unlock(&log->l_icloglock);
-	}
+	if (tail_lsn == 0)
+		tail_lsn = atomic64_read(&log->l_last_sync_lsn);
 
 	spin_lock(&log->l_grant_lock);
 
@@ -845,11 +841,9 @@ xlog_assign_tail_lsn(xfs_mount_t *mp)
 
 	tail_lsn = xfs_trans_ail_tail(mp->m_ail);
 	spin_lock(&log->l_grant_lock);
-	if (tail_lsn != 0) {
-		log->l_tail_lsn = tail_lsn;
-	} else {
-		tail_lsn = log->l_tail_lsn = log->l_last_sync_lsn;
-	}
+	if (!tail_lsn)
+		tail_lsn = atomic64_read(&log->l_last_sync_lsn);
+	log->l_tail_lsn = tail_lsn;
 	spin_unlock(&log->l_grant_lock);
 
 	return tail_lsn;
@@ -1057,10 +1051,9 @@ xlog_alloc_log(xfs_mount_t	*mp,
 	log->l_flags	   |= XLOG_ACTIVE_RECOVERY;
 
 	log->l_prev_block  = -1;
-	log->l_tail_lsn	   = xlog_assign_lsn(1, 0);
-	/* log->l_tail_lsn = 0x100000000LL; cycle = 1; current block = 0 */
-	log->l_last_sync_lsn = log->l_tail_lsn;
 	log->l_curr_cycle  = 1;	    /* 0 is bad since this is initial value */
+	log->l_tail_lsn	   = xlog_assign_lsn(1, 0);
+	atomic64_set(&log->l_last_sync_lsn, log->l_tail_lsn);
 	log->l_grant_reserve_lsn = xlog_assign_lsn(1, 0);
 	log->l_grant_write_lsn = xlog_assign_lsn(1, 0);
 	INIT_LIST_HEAD(&log->l_reserveq);
@@ -2241,7 +2234,7 @@ xlog_state_do_callback(
 				lowest_lsn = xlog_get_lowest_lsn(log);
 				if (lowest_lsn &&
 				    XFS_LSN_CMP(lowest_lsn,
-				    		be64_to_cpu(iclog->ic_header.h_lsn)) < 0) {
+						be64_to_cpu(iclog->ic_header.h_lsn)) < 0) {
 					iclog = iclog->ic_next;
 					continue; /* Leave this iclog for
 						   * another thread */
@@ -2249,23 +2242,21 @@ xlog_state_do_callback(
 
 				iclog->ic_state = XLOG_STATE_CALLBACK;
 
-				spin_unlock(&log->l_icloglock);
 
-				/* l_last_sync_lsn field protected by
-				 * l_grant_lock. Don't worry about iclog's lsn.
-				 * No one else can be here except us.
+				/*
+				 * update the last_sync_lsn before we drop the
+				 * icloglock to ensure we are the only one that
+				 * can update it.
 				 */
-				spin_lock(&log->l_grant_lock);
-				ASSERT(XFS_LSN_CMP(log->l_last_sync_lsn,
-				       be64_to_cpu(iclog->ic_header.h_lsn)) <= 0);
-				log->l_last_sync_lsn =
-					be64_to_cpu(iclog->ic_header.h_lsn);
-				spin_unlock(&log->l_grant_lock);
+				ASSERT(XFS_LSN_CMP(atomic64_read(&log->l_last_sync_lsn),
+					be64_to_cpu(iclog->ic_header.h_lsn)) <= 0);
+				atomic64_set(&log->l_last_sync_lsn,
+					be64_to_cpu(iclog->ic_header.h_lsn));
 
-			} else {
-				spin_unlock(&log->l_icloglock);
+			} else
 				ioerrors++;
-			}
+
+			spin_unlock(&log->l_icloglock);
 
 			/*
 			 * Keep processing entries in the callback list until
@@ -2576,7 +2567,8 @@ redo:
 			list_add_tail(&tic->t_queue, &log->l_reserveq);
 
 		xlog_grant_push_ail(log, log->l_tail_lsn,
-				    log->l_last_sync_lsn, need_bytes);
+				    atomic64_read(&log->l_last_sync_lsn),
+				    need_bytes);
 
 		XFS_STATS_INC(xs_sleep_logspace);
 		trace_xfs_log_grant_sleep(log, tic);
@@ -2683,7 +2675,8 @@ redo:
 		}
 
 		xlog_grant_push_ail(log, log->l_tail_lsn,
-				    log->l_last_sync_lsn, need_bytes);
+				    atomic64_read(&log->l_last_sync_lsn),
+				    need_bytes);
 
 		XFS_STATS_INC(xs_sleep_logspace);
 		trace_xfs_log_regrant_write_sleep(log, tic);
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index 6fcee10..97db8a8 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -508,7 +508,6 @@ typedef struct log {
 	spinlock_t		l_icloglock;    /* grab to change iclog state */
 	xfs_lsn_t		l_tail_lsn;     /* lsn of 1st LR with unflushed
 						 * buffers */
-	xfs_lsn_t		l_last_sync_lsn;/* lsn of last LR on disk */
 	int			l_curr_cycle;   /* Cycle number of log writes */
 	int			l_prev_cycle;   /* Cycle number before last
 						 * block increment */
@@ -522,6 +521,14 @@ typedef struct log {
 	xfs_lsn_t		l_grant_reserve_lsn;
 	xfs_lsn_t		l_grant_write_lsn;
 
+	/*
+	 * l_last_sync_lsn is an atomic so it can be set and read without
+	 * needing to hold specific locks. To avoid operations contending with
+	 * other hot objects, place it on a separate cacheline.
+	 */
+	/* lsn of last LR on disk */
+	atomic64_t		l_last_sync_lsn ____cacheline_aligned_in_smp;
+
 	/* The following field are used for debugging; need to hold icloglock */
 #ifdef DEBUG
 	char			*l_iclog_bak[XLOG_MAX_ICLOGS];
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index d8c62f0..2ce7b48 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -926,7 +926,7 @@ xlog_find_tail(
 	if (found == 2)
 		log->l_curr_cycle++;
 	log->l_tail_lsn = be64_to_cpu(rhead->h_tail_lsn);
-	log->l_last_sync_lsn = be64_to_cpu(rhead->h_lsn);
+	atomic64_set(&log->l_last_sync_lsn, be64_to_cpu(rhead->h_lsn));
 	log->l_grant_reserve_lsn = xlog_assign_lsn(log->l_curr_cycle,
 						BBTOB(log->l_curr_block));
 	log->l_grant_write_lsn = xlog_assign_lsn(log->l_curr_cycle,
@@ -978,9 +978,9 @@ xlog_find_tail(
 			log->l_tail_lsn =
 				xlog_assign_lsn(log->l_curr_cycle,
 						after_umount_blk);
-			log->l_last_sync_lsn =
+			atomic64_set(&log->l_last_sync_lsn,
 				xlog_assign_lsn(log->l_curr_cycle,
-						after_umount_blk);
+						after_umount_blk));
 			*tail_blk = after_umount_blk;
 
 			/*
-- 
1.7.2.3

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  parent reply	other threads:[~2010-11-29  1:37 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-11-29  1:38 [PATCH 0/14] xfs: grant lock scaling and removal V2 Dave Chinner
2010-11-29  1:38 ` [PATCH 01/14] xfs: convert log grant ticket queues to list heads Dave Chinner
2010-11-30 22:59   ` Christoph Hellwig
2010-11-29  1:38 ` [PATCH 02/14] xfs: clean up log space grant functions Dave Chinner
2010-12-01 12:30   ` Christoph Hellwig
2010-12-02  1:48     ` Dave Chinner
2010-12-02 11:40       ` Christoph Hellwig
2010-12-03  6:45         ` Dave Chinner
2010-11-29  1:38 ` [PATCH 03/14] xfs: convert log grant heads to LSN notation Dave Chinner
2010-12-01 12:42   ` Christoph Hellwig
2010-12-02  1:49     ` Dave Chinner
2010-12-01 13:05   ` Christoph Hellwig
2010-12-02  2:01     ` Dave Chinner
2010-12-02 11:47       ` Christoph Hellwig
2010-11-29  1:38 ` [PATCH 04/14] xfs: use wait queues directly for log grant queues Dave Chinner
2010-12-01 12:34   ` Christoph Hellwig
2010-12-02  2:02     ` Dave Chinner
2010-11-29  1:38 ` [PATCH 05/14] xfs: make AIL tail pushing independent of the grant lock Dave Chinner
2010-12-01 12:45   ` Christoph Hellwig
2010-12-02  2:04     ` Dave Chinner
2010-11-29  1:38 ` Dave Chinner [this message]
2010-12-01 12:54   ` [PATCH 06/14] xfs: convert l_last_sync_lsn to an atomic variable Christoph Hellwig
2010-11-29  1:38 ` [PATCH 07/14] xfs: convert l_tail_lsn " Dave Chinner
2010-12-01 12:56   ` Christoph Hellwig
2010-11-29  1:38 ` [PATCH 08/14] xfs: convert log grant heads to atomic variables Dave Chinner
2010-12-01 12:59   ` Christoph Hellwig
2010-12-02  2:04     ` Dave Chinner
2010-11-29  1:38 ` [PATCH 09/14] xfs: introduce new locks for the log grant ticket wait queues Dave Chinner
2010-12-01 13:12   ` Christoph Hellwig
2010-12-02  2:10     ` Dave Chinner
2010-12-02 11:48       ` Christoph Hellwig
2010-11-29  1:38 ` [PATCH 10/14] xfs: convert grant head manipulations to lockless algorithm Dave Chinner
2010-12-01 13:15   ` Christoph Hellwig
2010-12-02  2:11     ` Dave Chinner
2010-11-29  1:38 ` [PATCH 11/14] xfs: remove log grant lock Dave Chinner
2010-12-01 13:15   ` Christoph Hellwig
2010-11-29  1:38 ` [PATCH 12/14] xfs: kill useless spinlock_destroy macro Dave Chinner
2010-12-01 13:19   ` Christoph Hellwig
2010-11-29  1:38 ` [PATCH 13/14] xfs: replace use of sv_t with waitqueues in the log Dave Chinner
2010-12-01 13:20   ` Christoph Hellwig
2010-11-29  1:38 ` [PATCH 14/14] xfs: remove sv wrappers Dave Chinner
2010-12-01 13:20   ` Christoph Hellwig

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