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>
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index f75ab10..e3fcbea 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -283,6 +283,35 @@
nodelalloc Disable delayed allocation. Blocks are allocation
when data is copied from user to page cache.
+max_batch_time=usec Maximum amount of time ext4 should wait for
+ additional filesystem operations to be batch
+ together with a synchronous write operation.
+ Since a synchronous write operation is going to
+ force a commit and then a wait for the I/O
+ complete, it doesn't cost much, and can be a
+ huge throughput win, we wait for a small amount
+ of time to see if any other transactions can
+ piggyback on the synchronous write. The
+ algorithm used is designed to automatically tune
+ for the speed of the disk, by measuring the
+ amount of time (on average) that it takes to
+ finish committing a transaction. Call this time
+ the "commit time". If the time that the
+ transactoin has been running is less than the
+ commit time, ext4 will try sleeping for the
+ commit time to see if other operations will join
+ the transaction. The commit time is capped by
+ the max_batch_time, which defaults to 15000us
+ (15ms). This optimization can be turned off
+ entirely by setting max_batch_time to 0.
+
+min_batch_time=usec This parameter sets the commit time (as
+ described above) to be at least min_batch_time.
+ It defaults to zero microseconds. Increasing
+ this parameter may improve the throughput of
+ multi-threaded, synchronous workloads on very
+ fast disks, at the cost of increasing latency.
+
Data Mode
=========
There are 3 different data modes:
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index ac8551e0..9ba9fd6 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -328,6 +328,7 @@
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 @@
#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 3db800f..039b6ea 100644
--- a/fs/ext4/ext4_sb.h
+++ b/fs/ext4/ext4_sb.h
@@ -74,6 +74,8 @@
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 dc27d4c..da377f9 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -705,10 +705,19 @@
#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 @@
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 @@
{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 @@
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 @@
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 @@
{
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 @@
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 @@
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++) {
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 74d8729..fd1d755 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -964,6 +964,8 @@
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 13dcbc9..48c21ba 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1255,8 +1255,10 @@
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(),
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index ab8cef1..a3cd647 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -956,6 +956,14 @@
*/
u64 j_average_commit_time;
+ /*
+ * minimum and maximum times that we should wait for
+ * additional filesystem operations to get batched into a
+ * synchronous handle in microseconds
+ */
+ u32 j_min_batch_time;
+ u32 j_max_batch_time;
+
/* This function is called when a transaction is closed */
void (*j_commit_callback)(journal_t *,
transaction_t *);