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Commit 9fff24aa authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

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: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 40ae3487

fs/jbd2/commit.c

+8 −0
Original line number Diff line number Diff line
@@ -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 @@ void jbd2_journal_commit_transaction(journal_t *journal) 
	 */

	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;

fs/jbd2/journal.c

+9 −3
Original line number Diff line number Diff line
@@ -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,

	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",

fs/jbd2/transaction.c

+1 −0
Original line number Diff line number Diff line
@@ -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;

}

include/linux/jbd2.h

+7 −0
Original line number Diff line number Diff line
@@ -580,6 +580,11 @@ struct transaction_s 
	 */

	unsigned long		t_start;



	/*

	 * When commit was requested

	 */

	unsigned long		t_requested;



	/*

	 * Checkpointing stats [j_checkpoint_sem]

	 */
@@ -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;

};

include/trace/events/jbd2.h

+6 −2
Original line number Diff line number Diff line
@@ -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),