* [PATCH 2/6] jbd2: calculate statistics without holding j_state_lock and j_list_lock
2014-03-09 6:05 [PATCH 1/6] jbd2: don't hold j_state_lock while calling wake_up() Theodore Ts'o
@ 2014-03-09 6:05 ` Theodore Ts'o
2014-03-09 6:05 ` [PATCH 3/6] jbd2: add transaction to checkpoint list earlier Theodore Ts'o
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Theodore Ts'o @ 2014-03-09 6:05 UTC (permalink / raw)
To: Ext4 Developers List; +Cc: Theodore Ts'o
The two hottest locks, and thus the biggest scalability bottlenecks,
in the jbd2 layer, are the j_list_lock and j_state_lock. This has
inspired some people to do some truly unnatural things[1].
[1] https://www.usenix.org/system/files/conference/fast14/fast14-paper_kang.pdf
We don't need to be holding both j_state_lock and j_list_lock while
calculating the journal statistics, so move those calculations to the
very end of jbd2_journal_commit_transaction.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
fs/jbd2/commit.c | 36 ++++++++++++++++++------------------
1 file changed, 18 insertions(+), 18 deletions(-)
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 765b31d..af36252 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -1083,24 +1083,7 @@ restart_loop:
atomic_read(&commit_transaction->t_handle_count);
trace_jbd2_run_stats(journal->j_fs_dev->bd_dev,
commit_transaction->t_tid, &stats.run);
-
- /*
- * Calculate overall stats
- */
- spin_lock(&journal->j_history_lock);
- journal->j_stats.ts_tid++;
- if (commit_transaction->t_requested)
- journal->j_stats.ts_requested++;
- journal->j_stats.run.rs_wait += stats.run.rs_wait;
- journal->j_stats.run.rs_request_delay += stats.run.rs_request_delay;
- journal->j_stats.run.rs_running += stats.run.rs_running;
- journal->j_stats.run.rs_locked += stats.run.rs_locked;
- journal->j_stats.run.rs_flushing += stats.run.rs_flushing;
- journal->j_stats.run.rs_logging += stats.run.rs_logging;
- journal->j_stats.run.rs_handle_count += stats.run.rs_handle_count;
- journal->j_stats.run.rs_blocks += stats.run.rs_blocks;
- journal->j_stats.run.rs_blocks_logged += stats.run.rs_blocks_logged;
- spin_unlock(&journal->j_history_lock);
+ stats.ts_requested = (commit_transaction->t_requested) ? 1 : 0;
commit_transaction->t_state = T_COMMIT_CALLBACK;
J_ASSERT(commit_transaction == journal->j_committing_transaction);
@@ -1157,4 +1140,21 @@ restart_loop:
spin_unlock(&journal->j_list_lock);
write_unlock(&journal->j_state_lock);
wake_up(&journal->j_wait_done_commit);
+
+ /*
+ * Calculate overall stats
+ */
+ spin_lock(&journal->j_history_lock);
+ journal->j_stats.ts_tid++;
+ journal->j_stats.ts_requested += stats.ts_requested;
+ journal->j_stats.run.rs_wait += stats.run.rs_wait;
+ journal->j_stats.run.rs_request_delay += stats.run.rs_request_delay;
+ journal->j_stats.run.rs_running += stats.run.rs_running;
+ journal->j_stats.run.rs_locked += stats.run.rs_locked;
+ journal->j_stats.run.rs_flushing += stats.run.rs_flushing;
+ journal->j_stats.run.rs_logging += stats.run.rs_logging;
+ journal->j_stats.run.rs_handle_count += stats.run.rs_handle_count;
+ journal->j_stats.run.rs_blocks += stats.run.rs_blocks;
+ journal->j_stats.run.rs_blocks_logged += stats.run.rs_blocks_logged;
+ spin_unlock(&journal->j_history_lock);
}
--
1.9.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH 3/6] jbd2: add transaction to checkpoint list earlier
2014-03-09 6:05 [PATCH 1/6] jbd2: don't hold j_state_lock while calling wake_up() Theodore Ts'o
2014-03-09 6:05 ` [PATCH 2/6] jbd2: calculate statistics without holding j_state_lock and j_list_lock Theodore Ts'o
@ 2014-03-09 6:05 ` Theodore Ts'o
2014-03-09 6:05 ` [PATCH 4/6] jbd2: check jh->b_transaction without taking j_list_lock Theodore Ts'o
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Theodore Ts'o @ 2014-03-09 6:05 UTC (permalink / raw)
To: Ext4 Developers List; +Cc: Theodore Ts'o
We don't otherwise need j_list_lock during the rest of commit phase
#7, so add the transaction to the checkpoint list at the very end of
commit phase #6. This allows us to drop j_list_lock earlier, which is
a good thing since it is a super hot lock.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
fs/jbd2/commit.c | 39 ++++++++++++++++++++-------------------
1 file changed, 20 insertions(+), 19 deletions(-)
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index af36252..5f26139 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -1065,6 +1065,25 @@ restart_loop:
goto restart_loop;
}
+ /* Add the transaction to the checkpoint list
+ * __journal_remove_checkpoint() can not destroy transaction
+ * under us because it is not marked as T_FINISHED yet */
+ if (journal->j_checkpoint_transactions == NULL) {
+ journal->j_checkpoint_transactions = commit_transaction;
+ commit_transaction->t_cpnext = commit_transaction;
+ commit_transaction->t_cpprev = commit_transaction;
+ } else {
+ commit_transaction->t_cpnext =
+ journal->j_checkpoint_transactions;
+ commit_transaction->t_cpprev =
+ commit_transaction->t_cpnext->t_cpprev;
+ commit_transaction->t_cpnext->t_cpprev =
+ commit_transaction;
+ commit_transaction->t_cpprev->t_cpnext =
+ commit_transaction;
+ }
+ spin_unlock(&journal->j_list_lock);
+
/* Done with this transaction! */
jbd_debug(3, "JBD2: commit phase 7\n");
@@ -1103,24 +1122,6 @@ restart_loop:
write_unlock(&journal->j_state_lock);
- if (journal->j_checkpoint_transactions == NULL) {
- journal->j_checkpoint_transactions = commit_transaction;
- commit_transaction->t_cpnext = commit_transaction;
- commit_transaction->t_cpprev = commit_transaction;
- } else {
- commit_transaction->t_cpnext =
- journal->j_checkpoint_transactions;
- commit_transaction->t_cpprev =
- commit_transaction->t_cpnext->t_cpprev;
- commit_transaction->t_cpnext->t_cpprev =
- commit_transaction;
- commit_transaction->t_cpprev->t_cpnext =
- commit_transaction;
- }
- spin_unlock(&journal->j_list_lock);
- /* Drop all spin_locks because commit_callback may be block.
- * __journal_remove_checkpoint() can not destroy transaction
- * under us because it is not marked as T_FINISHED yet */
if (journal->j_commit_callback)
journal->j_commit_callback(journal, commit_transaction);
@@ -1131,7 +1132,7 @@ restart_loop:
write_lock(&journal->j_state_lock);
spin_lock(&journal->j_list_lock);
commit_transaction->t_state = T_FINISHED;
- /* Recheck checkpoint lists after j_list_lock was dropped */
+ /* Check if the transaction can be dropped now that we are finished */
if (commit_transaction->t_checkpoint_list == NULL &&
commit_transaction->t_checkpoint_io_list == NULL) {
__jbd2_journal_drop_transaction(journal, commit_transaction);
--
1.9.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH 4/6] jbd2: check jh->b_transaction without taking j_list_lock
2014-03-09 6:05 [PATCH 1/6] jbd2: don't hold j_state_lock while calling wake_up() Theodore Ts'o
2014-03-09 6:05 ` [PATCH 2/6] jbd2: calculate statistics without holding j_state_lock and j_list_lock Theodore Ts'o
2014-03-09 6:05 ` [PATCH 3/6] jbd2: add transaction to checkpoint list earlier Theodore Ts'o
@ 2014-03-09 6:05 ` Theodore Ts'o
2014-03-09 6:05 ` [PATCH 5/6] jbd2: minimize region locked by j_list_lock in journal_get_create_access() Theodore Ts'o
2014-03-09 6:05 ` [PATCH 6/6] jbd2: minimize region locked by j_list_lock in jbd2_journal_forget() Theodore Ts'o
4 siblings, 0 replies; 6+ messages in thread
From: Theodore Ts'o @ 2014-03-09 6:05 UTC (permalink / raw)
To: Ext4 Developers List; +Cc: Theodore Ts'o
jh->b_transaction is adequately protected for reading by the
jbd_lock_bh_state(bh), so we don't need to take j_list_lock in
__journal_try_to_free_buffer().
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
fs/jbd2/transaction.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 60bb365..78900a1 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1821,11 +1821,11 @@ __journal_try_to_free_buffer(journal_t *journal, struct buffer_head *bh)
if (buffer_locked(bh) || buffer_dirty(bh))
goto out;
- if (jh->b_next_transaction != NULL)
+ if (jh->b_next_transaction != NULL || jh->b_transaction != NULL)
goto out;
spin_lock(&journal->j_list_lock);
- if (jh->b_cp_transaction != NULL && jh->b_transaction == NULL) {
+ if (jh->b_cp_transaction != NULL) {
/* written-back checkpointed metadata buffer */
JBUFFER_TRACE(jh, "remove from checkpoint list");
__jbd2_journal_remove_checkpoint(jh);
--
1.9.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH 5/6] jbd2: minimize region locked by j_list_lock in journal_get_create_access()
2014-03-09 6:05 [PATCH 1/6] jbd2: don't hold j_state_lock while calling wake_up() Theodore Ts'o
` (2 preceding siblings ...)
2014-03-09 6:05 ` [PATCH 4/6] jbd2: check jh->b_transaction without taking j_list_lock Theodore Ts'o
@ 2014-03-09 6:05 ` Theodore Ts'o
2014-03-09 6:05 ` [PATCH 6/6] jbd2: minimize region locked by j_list_lock in jbd2_journal_forget() Theodore Ts'o
4 siblings, 0 replies; 6+ messages in thread
From: Theodore Ts'o @ 2014-03-09 6:05 UTC (permalink / raw)
To: Ext4 Developers List; +Cc: Theodore Ts'o
It's not needed until we start trying to modifying fields in the
journal_head which are protected by j_list_lock.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
fs/jbd2/transaction.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 78900a1..357f3dc 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1073,7 +1073,6 @@ int jbd2_journal_get_create_access(handle_t *handle, struct buffer_head *bh)
* reused here.
*/
jbd_lock_bh_state(bh);
- spin_lock(&journal->j_list_lock);
J_ASSERT_JH(jh, (jh->b_transaction == transaction ||
jh->b_transaction == NULL ||
(jh->b_transaction == journal->j_committing_transaction &&
@@ -1096,12 +1095,14 @@ int jbd2_journal_get_create_access(handle_t *handle, struct buffer_head *bh)
jh->b_modified = 0;
JBUFFER_TRACE(jh, "file as BJ_Reserved");
+ spin_lock(&journal->j_list_lock);
__jbd2_journal_file_buffer(jh, transaction, BJ_Reserved);
} else if (jh->b_transaction == journal->j_committing_transaction) {
/* first access by this transaction */
jh->b_modified = 0;
JBUFFER_TRACE(jh, "set next transaction");
+ spin_lock(&journal->j_list_lock);
jh->b_next_transaction = transaction;
}
spin_unlock(&journal->j_list_lock);
--
1.9.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH 6/6] jbd2: minimize region locked by j_list_lock in jbd2_journal_forget()
2014-03-09 6:05 [PATCH 1/6] jbd2: don't hold j_state_lock while calling wake_up() Theodore Ts'o
` (3 preceding siblings ...)
2014-03-09 6:05 ` [PATCH 5/6] jbd2: minimize region locked by j_list_lock in journal_get_create_access() Theodore Ts'o
@ 2014-03-09 6:05 ` Theodore Ts'o
4 siblings, 0 replies; 6+ messages in thread
From: Theodore Ts'o @ 2014-03-09 6:05 UTC (permalink / raw)
To: Ext4 Developers List; +Cc: Theodore Ts'o
It's not needed until we start trying to modifying fields in the
journal_head which are protected by j_list_lock.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
fs/jbd2/transaction.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 357f3dc..d999b1f 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1416,7 +1416,6 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
BUFFER_TRACE(bh, "entry");
jbd_lock_bh_state(bh);
- spin_lock(&journal->j_list_lock);
if (!buffer_jbd(bh))
goto not_jbd;
@@ -1469,6 +1468,7 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
* we know to remove the checkpoint after we commit.
*/
+ spin_lock(&journal->j_list_lock);
if (jh->b_cp_transaction) {
__jbd2_journal_temp_unlink_buffer(jh);
__jbd2_journal_file_buffer(jh, transaction, BJ_Forget);
@@ -1481,6 +1481,7 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
goto drop;
}
}
+ spin_unlock(&journal->j_list_lock);
} else if (jh->b_transaction) {
J_ASSERT_JH(jh, (jh->b_transaction ==
journal->j_committing_transaction));
@@ -1492,7 +1493,9 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
if (jh->b_next_transaction) {
J_ASSERT(jh->b_next_transaction == transaction);
+ spin_lock(&journal->j_list_lock);
jh->b_next_transaction = NULL;
+ spin_unlock(&journal->j_list_lock);
/*
* only drop a reference if this transaction modified
@@ -1504,7 +1507,6 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
}
not_jbd:
- spin_unlock(&journal->j_list_lock);
jbd_unlock_bh_state(bh);
__brelse(bh);
drop:
--
1.9.0
^ permalink raw reply related [flat|nested] 6+ messages in thread