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Date: Tue, 21 Apr 2015 12:03:49 -0400
From: Hung-Ching Chang <hcchang@...edu>
To: "Theodore Ts'o" <tytso@....edu>,
Andreas Dilger <adilger.kernel@...ger.ca>
Cc: linux-ext4@...r.kernel.org, Hung-Ching Chang <hcchang@...edu>
Subject: [PATCH 1/1] ext4/jbd2: Force copy-outs during metadata commiting
The do_get_write_access()(fs/jbd2/transaction.c) may have to wait on the buffer that is being flushed out by the committing transaction and has not yet made the copy-out by the current transaction. When such condition is true, do_get_write_access() has to wait until BH_Shadow is cleared, which could take a very long time because of waiting on IO. In our research*, we observed that this situation become worse on parallel-transactional workloads (Filbebench** OLTP and IOzone*** write tests) to the ext4 filesystem. This patch forces copy-out to enable, and can be configured on the fly via /sys/fs/ext4/<device>/force_copyout. Our experimental results*, with force copy-out, showed ~25% speedup on Filebench OLTP and ~3X speedup on IOzone.
*Hung-Ching Chang, Bo Li, Godmar Back, Ali R. Butt, Kirk W. Cameron, "LUC: Limiting the Unintended Consequences of Power Scaling on Parallel Transaction-oriented Workloads," accepted by in proceedings of 29th IEEE International Parallel & Distributed Processing Symposium (IPDPS), Hyderabad, INDIA, 2015.
**http://filebench.sourceforge.net/
***http://www.iozone.org
Signed-off-by: Hung-Ching Chang <hcchang@...edu>
---
Documentation/filesystems/ext4.txt | 11 +++++++++++
fs/ext4/ext4.h | 6 ++++++
fs/ext4/super.c | 26 ++++++++++++++++++++++++++
fs/jbd2/journal.c | 2 ++
include/linux/jbd2.h | 7 +++++++
5 files changed, 52 insertions(+), 0 deletions(-)
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 6c0108e..8282959 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -510,6 +510,17 @@ Files in /sys/fs/ext4/<devname>
in the file system. If there is not enough space
for the reserved space when mounting the file
mount will _not_ fail.
+
+ force_copyout=<0|1(*)> This enables/disables the force copyout in the
+ jbd code. force_copyout=0 disables,
+ force_copyout=1 enables. When enabled, the
+ committing transaction makes copy-outs for the
+ metadata for IO submission. This removes
+ potential locks when the current transaction
+ attempts to modify the metadata, which are also
+ owned by the committing transaction and are
+ being flushed out to non-volatile storage, but
+ copy-outs have not yet made for these metadata.
..............................................................................
Ioctls
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index f63c3d5..585836f 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1247,6 +1247,7 @@ struct ext4_sb_info {
unsigned long s_commit_interval;
u32 s_max_batch_time;
u32 s_min_batch_time;
+ u32 s_force_copyout;
struct block_device *journal_bdev;
#ifdef CONFIG_QUOTA
char *s_qf_names[EXT4_MAXQUOTAS]; /* Names of quota files with journalled quota */
@@ -1620,6 +1621,11 @@ static inline void ext4_clear_state_flags(struct ext4_inode_info *ei)
#define EXT4_DEF_MAX_BATCH_TIME 15000 /* 15ms */
/*
+ * Default force copyout is set to enable
+ */
+#define EXT4_DEF_FORCE_COPYOUT 1
+
+/*
* Minimum number of groups in a flexgroup before we separate out
* directories into the first block group of a flexgroup
*/
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index e061e66..e09f7d2 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2508,6 +2508,27 @@ static ssize_t inode_readahead_blks_store(struct ext4_attr *a,
return count;
}
+static ssize_t force_copyout_store(struct ext4_attr *a,
+ struct ext4_sb_info *sbi,
+ const char *buf, size_t count)
+{
+ journal_t *journal = sbi->s_journal;
+ unsigned long t;
+ int ret;
+
+ ret = kstrtoul(skip_spaces(buf), 0, &t);
+ if (ret)
+ return ret;
+
+ if (t >= 2)
+ return -EINVAL;
+
+ sbi->s_force_copyout = t;
+ if (journal)
+ journal->j_force_copyout = sbi->s_force_copyout;
+ return count;
+}
+
static ssize_t sbi_ui_show(struct ext4_attr *a,
struct ext4_sb_info *sbi, char *buf)
{
@@ -2652,6 +2673,8 @@ EXT4_RW_ATTR_SBI_UI(msg_ratelimit_burst, s_msg_ratelimit_state.burst);
EXT4_RO_ATTR_ES_UI(errors_count, s_error_count);
EXT4_RO_ATTR_ES_UI(first_error_time, s_first_error_time);
EXT4_RO_ATTR_ES_UI(last_error_time, s_last_error_time);
+EXT4_ATTR_OFFSET(force_copyout, 0644, sbi_ui_show,
+ force_copyout_store, s_force_copyout);
static struct attribute *ext4_attrs[] = {
ATTR_LIST(delayed_allocation_blocks),
@@ -2678,6 +2701,7 @@ static struct attribute *ext4_attrs[] = {
ATTR_LIST(errors_count),
ATTR_LIST(first_error_time),
ATTR_LIST(last_error_time),
+ ATTR_LIST(force_copyout),
NULL,
};
@@ -3444,6 +3468,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
sb->s_fs_info = sbi;
sbi->s_sb = sb;
sbi->s_inode_readahead_blks = EXT4_DEF_INODE_READAHEAD_BLKS;
+ sbi->s_force_copyout = EXT4_DEF_FORCE_COPYOUT;
sbi->s_sb_block = sb_block;
if (sb->s_bdev->bd_part)
sbi->s_sectors_written_start =
@@ -4321,6 +4346,7 @@ static void ext4_init_journal_params(struct super_block *sb, journal_t *journal)
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;
+ journal->j_force_copyout = sbi->s_force_copyout;
write_lock(&journal->j_state_lock);
if (test_opt(sb, BARRIER))
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index b96bd80..2637234 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -396,6 +396,8 @@ repeat:
new_page = virt_to_page(jh_in->b_frozen_data);
new_offset = offset_in_page(jh_in->b_frozen_data);
} else {
+ if (journal->j_force_copyout == 1)
+ need_copy_out = 1; /* pessimistically copy data out */
new_page = jh2bh(jh_in)->b_page;
new_offset = offset_in_page(jh2bh(jh_in)->b_data);
}
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 20e7f78..eb72346 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -968,6 +968,13 @@ struct journal_s
u32 j_min_batch_time;
u32 j_max_batch_time;
+ /*
+ * when force_copyout is set to enable(1), the committing
+ * transaction makes copy-outs for the metadata and uses the copied
+ * buffers for IO submission.
+ */
+ u32 j_force_copyout;
+
/* This function is called when a transaction is closed */
void (*j_commit_callback)(journal_t *,
transaction_t *);
--
1.7.1
--
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