ext4: add fsync batch tuning knobs

Add new mount options, min_batch_time and max_batch_time, which
controls how long the jbd2 layer should wait for additional filesystem
operations to get batched with a synchronous write transaction.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

2 files changed, 5 insertions, 1 deletions

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 74d87290381c..fd1d7557a098 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -964,6 +964,8 @@ static journal_t * journal_init_common (void)
         spin_lock_init(&journal->j_state_lock);
 
         journal->j_commit_interval = (HZ * JBD2_DEFAULT_MAX_COMMIT_AGE);
+        journal->j_min_batch_time = 0;
+        journal->j_max_batch_time = 15000; /* 15ms */
 
         /* The journal is marked for error until we succeed with recovery! */
         journal->j_flags = JBD2_ABORT;
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 13dcbc990f41..48c21bac5a56 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1255,8 +1255,10 @@ int jbd2_journal_stop(handle_t *handle)
                 trans_time = ktime_to_ns(ktime_sub(ktime_get(),
                                                    transaction->t_start_time));
 
+                commit_time = max_t(u64, commit_time,
+                                    1000*journal->j_min_batch_time);
                 commit_time = min_t(u64, commit_time,
-                                    1000*jiffies_to_usecs(1));
+                                    1000*journal->j_max_batch_time);
 
                 if (trans_time < commit_time) {
                         ktime_t expires = ktime_add_ns(ktime_get(),