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>

3 files changed, 49 insertions, 7 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index ac8551e0b70a..9ba9fd6d14da 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -328,6 +328,7 @@ struct ext4_mount_options {
         uid_t s_resuid;
         gid_t s_resgid;
         unsigned long s_commit_interval;
+        u32 s_min_batch_time, s_max_batch_time;
 #ifdef CONFIG_QUOTA
         int s_jquota_fmt;
         char *s_qf_names[MAXQUOTAS];
@@ -806,6 +807,12 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino)
 #define EXT4_DEFM_JMODE_WBACK   0x0060
 
 /*
+ * Default journal batch times
+ */
+#define EXT4_DEF_MIN_BATCH_TIME 0
+#define EXT4_DEF_MAX_BATCH_TIME 15000 /* 15ms */
+
+/*
  * Structure of a directory entry
  */
 #define EXT4_NAME_LEN 255
diff --git a/fs/ext4/ext4_sb.h b/fs/ext4/ext4_sb.h
index 3db800f399a6..039b6ea1a042 100644
--- a/fs/ext4/ext4_sb.h
+++ b/fs/ext4/ext4_sb.h
@@ -74,6 +74,8 @@ struct ext4_sb_info {
         struct journal_s *s_journal;
         struct list_head s_orphan;
         unsigned long s_commit_interval;
+        u32 s_max_batch_time;
+        u32 s_min_batch_time;
         struct block_device *journal_bdev;
 #ifdef CONFIG_JBD2_DEBUG
         struct timer_list turn_ro_timer;        /* For turning read-only (crash simulation) */
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index dc27d4c613c0..da377f9521bb 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -705,10 +705,19 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
 #endif
         if (!test_opt(sb, RESERVATION))
                 seq_puts(seq, ",noreservation");
-        if (sbi->s_commit_interval) {
+        if (sbi->s_commit_interval != JBD2_DEFAULT_MAX_COMMIT_AGE*HZ) {
                 seq_printf(seq, ",commit=%u",
                            (unsigned) (sbi->s_commit_interval / HZ));
         }
+        if (sbi->s_min_batch_time != EXT4_DEF_MIN_BATCH_TIME) {
+                seq_printf(seq, ",min_batch_time=%u",
+                           (unsigned) sbi->s_min_batch_time);
+        }
+        if (sbi->s_max_batch_time != EXT4_DEF_MAX_BATCH_TIME) {
+                seq_printf(seq, ",max_batch_time=%u",
+                           (unsigned) sbi->s_min_batch_time);
+        }
+
         /*
          * We're changing the default of barrier mount option, so
          * let's always display its mount state so it's clear what its
@@ -874,7 +883,8 @@ enum {
         Opt_nouid32, Opt_debug, Opt_oldalloc, Opt_orlov,
         Opt_user_xattr, Opt_nouser_xattr, Opt_acl, Opt_noacl,
         Opt_reservation, Opt_noreservation, Opt_noload, Opt_nobh, Opt_bh,
-        Opt_commit, Opt_journal_update, Opt_journal_inum, Opt_journal_dev,
+        Opt_commit, Opt_min_batch_time, Opt_max_batch_time,
+        Opt_journal_update, Opt_journal_inum, Opt_journal_dev,
         Opt_journal_checksum, Opt_journal_async_commit,
         Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback,
         Opt_data_err_abort, Opt_data_err_ignore,
@@ -913,6 +923,8 @@ static const match_table_t tokens = {
         {Opt_nobh, "nobh"},
         {Opt_bh, "bh"},
         {Opt_commit, "commit=%u"},
+        {Opt_min_batch_time, "min_batch_time=%u"},
+        {Opt_max_batch_time, "max_batch_time=%u"},
         {Opt_journal_update, "journal=update"},
         {Opt_journal_inum, "journal=%u"},
         {Opt_journal_dev, "journal_dev=%u"},
@@ -1131,6 +1143,22 @@ static int parse_options(char *options, struct super_block *sb,
                                 option = JBD2_DEFAULT_MAX_COMMIT_AGE;
                         sbi->s_commit_interval = HZ * option;
                         break;
+                case Opt_max_batch_time:
+                        if (match_int(&args[0], &option))
+                                return 0;
+                        if (option < 0)
+                                return 0;
+                        if (option == 0)
+                                option = EXT4_DEF_MAX_BATCH_TIME;
+                        sbi->s_max_batch_time = option;
+                        break;
+                case Opt_min_batch_time:
+                        if (match_int(&args[0], &option))
+                                return 0;
+                        if (option < 0)
+                                return 0;
+                        sbi->s_min_batch_time = option;
+                        break;
                 case Opt_data_journal:
                         data_opt = EXT4_MOUNT_JOURNAL_DATA;
                         goto datacheck;
@@ -1979,6 +2007,9 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 
         sbi->s_resuid = le16_to_cpu(es->s_def_resuid);
         sbi->s_resgid = le16_to_cpu(es->s_def_resgid);
+        sbi->s_commit_interval = JBD2_DEFAULT_MAX_COMMIT_AGE * HZ;
+        sbi->s_min_batch_time = EXT4_DEF_MIN_BATCH_TIME;
+        sbi->s_max_batch_time = EXT4_DEF_MAX_BATCH_TIME;
 
         set_opt(sbi->s_mount_opt, RESERVATION);
         set_opt(sbi->s_mount_opt, BARRIER);
@@ -2524,11 +2555,9 @@ static void ext4_init_journal_params(struct super_block *sb, journal_t *journal)
 {
         struct ext4_sb_info *sbi = EXT4_SB(sb);
 
-        if (sbi->s_commit_interval)
-                journal->j_commit_interval = sbi->s_commit_interval;
-        /* We could also set up an ext4-specific default for the commit
-         * interval here, but for now we'll just fall back to the jbd
-         * default. */
+        journal->j_commit_interval = sbi->s_commit_interval;
+        journal->j_min_batch_time = sbi->s_min_batch_time;
+        journal->j_max_batch_time = sbi->s_max_batch_time;
 
         spin_lock(&journal->j_state_lock);
         if (test_opt(sb, BARRIER))
@@ -3042,6 +3071,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
         old_opts.s_resuid = sbi->s_resuid;
         old_opts.s_resgid = sbi->s_resgid;
         old_opts.s_commit_interval = sbi->s_commit_interval;
+        old_opts.s_min_batch_time = sbi->s_min_batch_time;
+        old_opts.s_max_batch_time = sbi->s_max_batch_time;
 #ifdef CONFIG_QUOTA
         old_opts.s_jquota_fmt = sbi->s_jquota_fmt;
         for (i = 0; i < MAXQUOTAS; i++)
@@ -3178,6 +3209,8 @@ restore_opts:
         sbi->s_resuid = old_opts.s_resuid;
         sbi->s_resgid = old_opts.s_resgid;
         sbi->s_commit_interval = old_opts.s_commit_interval;
+        sbi->s_min_batch_time = old_opts.s_min_batch_time;
+        sbi->s_max_batch_time = old_opts.s_max_batch_time;
 #ifdef CONFIG_QUOTA
         sbi->s_jquota_fmt = old_opts.s_jquota_fmt;
         for (i = 0; i < MAXQUOTAS; i++) {