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@mit.edu>
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 @@
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 @@
*/
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 @@
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 @@
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 @@
journal->j_running_transaction = transaction;
transaction->t_max_wait = 0;
transaction->t_start = jiffies;
+ transaction->t_requested = 0;
return transaction;
}