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Commit 30773840 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

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: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent d7cfa468

Documentation/filesystems/ext4.txt

+29 −0
Original line number Diff line number Diff line
@@ -283,6 +283,35 @@ delalloc (*) Deferring block allocation until write-out time. 
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:

fs/ext4/ext4.h

+7 −0
Original line number Diff line number Diff line
@@ -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];
@@ -805,6 +806,12 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino) 
#define EXT4_DEFM_JMODE_ORDERED	0x0040

#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

 */

fs/ext4/ext4_sb.h

+2 −0
Original line number Diff line number Diff line
@@ -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) */

fs/ext4/super.c

+40 −7
Original line number Diff line number Diff line
@@ -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_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 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data) 
	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++) {

fs/jbd2/journal.c

+2 −0
Original line number Diff line number Diff line
@@ -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;