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Date: Sat, 9 Feb 2013 16:53:41 -0500
From: Theodore Ts'o <tytso@....edu>
To: Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc: Theodore Ts'o <tytso@....edu>
Subject: [PATCH 01/12] jbd2: track request delay statistics
Track the delay between when we first request that the commit begin
and when it actually begins, so we can see how much of a gap exists.
In theory, this should just be the remaining scheduling quantuum of
the thread which requested the commit (assuming it was not a
synchronous operation which triggered the commit request) plus
scheduling overhead; however, it's possible that real time processes
might get in the way of letting the kjournald thread from executing.
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
---
fs/jbd2/commit.c | 8 ++++++++
fs/jbd2/journal.c | 12 +++++++++---
fs/jbd2/transaction.c | 1 +
include/linux/jbd2.h | 7 +++++++
include/trace/events/jbd2.h | 8 ++++++--
5 files changed, 31 insertions(+), 5 deletions(-)
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 3091d42..750c701 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -435,7 +435,12 @@ void jbd2_journal_commit_transaction(journal_t *journal)
trace_jbd2_commit_locking(journal, commit_transaction);
stats.run.rs_wait = commit_transaction->t_max_wait;
+ stats.run.rs_request_delay = 0;
stats.run.rs_locked = jiffies;
+ if (commit_transaction->t_requested)
+ stats.run.rs_request_delay =
+ jbd2_time_diff(commit_transaction->t_requested,
+ stats.run.rs_locked);
stats.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
stats.run.rs_locked);
@@ -1116,7 +1121,10 @@ restart_loop:
*/
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;
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 1a80e31..4ba2e81 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -533,6 +533,7 @@ int __jbd2_log_start_commit(journal_t *journal, tid_t target)
jbd_debug(1, "JBD2: requesting commit %d/%d\n",
journal->j_commit_request,
journal->j_commit_sequence);
+ journal->j_running_transaction->t_requested = jiffies;
wake_up(&journal->j_wait_commit);
return 1;
} else if (!tid_geq(journal->j_commit_request, target))
@@ -898,13 +899,18 @@ static int jbd2_seq_info_show(struct seq_file *seq, void *v)
if (v != SEQ_START_TOKEN)
return 0;
- seq_printf(seq, "%lu transaction, each up to %u blocks\n",
- s->stats->ts_tid,
- s->journal->j_max_transaction_buffers);
+ seq_printf(seq, "%lu transactions (%lu requested), "
+ "each up to %u blocks\n",
+ s->stats->ts_tid, s->stats->ts_requested,
+ s->journal->j_max_transaction_buffers);
if (s->stats->ts_tid == 0)
return 0;
seq_printf(seq, "average: \n %ums waiting for transaction\n",
jiffies_to_msecs(s->stats->run.rs_wait / s->stats->ts_tid));
+ seq_printf(seq, " %ums request delay\n",
+ (s->stats->ts_requested == 0) ? 0 :
+ jiffies_to_msecs(s->stats->run.rs_request_delay /
+ s->stats->ts_requested));
seq_printf(seq, " %ums running transaction\n",
jiffies_to_msecs(s->stats->run.rs_running / s->stats->ts_tid));
seq_printf(seq, " %ums transaction was being locked\n",
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index df9f297..735609e 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -100,6 +100,7 @@ jbd2_get_transaction(journal_t *journal, transaction_t *transaction)
journal->j_running_transaction = transaction;
transaction->t_max_wait = 0;
transaction->t_start = jiffies;
+ transaction->t_requested = 0;
return transaction;
}
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index e30b663..e0aafc4 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -581,6 +581,11 @@ struct transaction_s
unsigned long t_start;
/*
+ * When commit was requested
+ */
+ unsigned long t_requested;
+
+ /*
* Checkpointing stats [j_checkpoint_sem]
*/
struct transaction_chp_stats_s t_chp_stats;
@@ -637,6 +642,7 @@ struct transaction_s
struct transaction_run_stats_s {
unsigned long rs_wait;
+ unsigned long rs_request_delay;
unsigned long rs_running;
unsigned long rs_locked;
unsigned long rs_flushing;
@@ -649,6 +655,7 @@ struct transaction_run_stats_s {
struct transaction_stats_s {
unsigned long ts_tid;
+ unsigned long ts_requested;
struct transaction_run_stats_s run;
};
diff --git a/include/trace/events/jbd2.h b/include/trace/events/jbd2.h
index 127993d..5419f57 100644
--- a/include/trace/events/jbd2.h
+++ b/include/trace/events/jbd2.h
@@ -142,6 +142,7 @@ TRACE_EVENT(jbd2_run_stats,
__field( dev_t, dev )
__field( unsigned long, tid )
__field( unsigned long, wait )
+ __field( unsigned long, request_delay )
__field( unsigned long, running )
__field( unsigned long, locked )
__field( unsigned long, flushing )
@@ -155,6 +156,7 @@ TRACE_EVENT(jbd2_run_stats,
__entry->dev = dev;
__entry->tid = tid;
__entry->wait = stats->rs_wait;
+ __entry->request_delay = stats->rs_request_delay;
__entry->running = stats->rs_running;
__entry->locked = stats->rs_locked;
__entry->flushing = stats->rs_flushing;
@@ -164,10 +166,12 @@ TRACE_EVENT(jbd2_run_stats,
__entry->blocks_logged = stats->rs_blocks_logged;
),
- TP_printk("dev %d,%d tid %lu wait %u running %u locked %u flushing %u "
- "logging %u handle_count %u blocks %u blocks_logged %u",
+ TP_printk("dev %d,%d tid %lu wait %u request_delay %u running %u "
+ "locked %u flushing %u logging %u handle_count %u "
+ "blocks %u blocks_logged %u",
MAJOR(__entry->dev), MINOR(__entry->dev), __entry->tid,
jiffies_to_msecs(__entry->wait),
+ jiffies_to_msecs(__entry->request_delay),
jiffies_to_msecs(__entry->running),
jiffies_to_msecs(__entry->locked),
jiffies_to_msecs(__entry->flushing),
--
1.7.12.rc0.22.gcdd159b
--
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