Some storage devices show relatively high latencies to complete cache_flush
commands, even though their normal IO speed is prettry much high. In such
the case, it needs to merge cache_flush commands as much as possible to avoid
issuing them redundantly.
So, this patch introduces a mount option, "-o flush_merge", to mitigate such
the overhead.
If this option is enabled by user, F2FS merges the cache_flush commands and then
issues just one cache_flush on behalf of them. Once the single command is
finished, F2FS sends a completion signal to all the pending threads.
Note that, this option can be used under a workload consisting of very intensive
concurrent fsync calls, while the storage handles cache_flush commands slowly.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@xxxxxxxxxxx>
---
Documentation/filesystems/f2fs.txt | 4 ++
fs/f2fs/f2fs.h | 16 +++++++
fs/f2fs/file.c | 2 +-
fs/f2fs/segment.c | 87 ++++++++++++++++++++++++++++++++++++++
fs/f2fs/super.c | 7 +++
5 files changed, 115 insertions(+), 1 deletion(-)
diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
index 2f6d021..25311e11 100644
--- a/Documentation/filesystems/f2fs.txt
+++ b/Documentation/filesystems/f2fs.txt
@@ -122,6 +122,10 @@ disable_ext_identify Disable the extension list configured by mkfs, so f2fs
inline_xattr Enable the inline xattrs feature.
inline_data Enable the inline data feature: New created small(<~3.4k)
files can be written into inode block.
+flush_merge Merge concurrent cache_flush commands as much as possible
+ to eliminate redundant command issues. If the underlying
+ device handles the cache_flush command relatively slowly,
+ recommend to enable this option.
================================================================================
DEBUGFS ENTRIES
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 1e3d869..2ecac83 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -40,6 +40,7 @@
#define F2FS_MOUNT_DISABLE_EXT_IDENTIFY 0x00000040
#define F2FS_MOUNT_INLINE_XATTR 0x00000080
#define F2FS_MOUNT_INLINE_DATA 0x00000100
+#define F2FS_MOUNT_FLUSH_MERGE 0x00000200
#define clear_opt(sbi, option) (sbi->mount_opt.opt &= ~F2FS_MOUNT_##option)
#define set_opt(sbi, option) (sbi->mount_opt.opt |= F2FS_MOUNT_##option)
@@ -316,6 +317,12 @@ enum {
NO_CHECK_TYPE
};
+struct flush_cmd {
+ struct flush_cmd *next;
+ struct completion wait;
+ int ret;
+};
+
struct f2fs_sm_info {
struct sit_info *sit_info; /* whole segment information */
struct free_segmap_info *free_info; /* free segment information */
@@ -344,6 +351,14 @@ struct f2fs_sm_info {
unsigned int ipu_policy; /* in-place-update policy */
unsigned int min_ipu_util; /* in-place-update threshold */
+
+ /* for flush command control */
+ struct task_struct *f2fs_issue_flush; /* flush thread */
+ wait_queue_head_t flush_wait_queue; /* waiting queue for wake-up */
+ struct flush_cmd *issue_list; /* list for command issue */
+ struct flush_cmd *dispatch_list; /* list for command dispatch */
+ spinlock_t issue_lock; /* for issue list lock */
+ struct flush_cmd *issue_tail; /* list tail of issue list */
};
/*
@@ -1160,6 +1175,7 @@ void destroy_node_manager_caches(void);
*/
void f2fs_balance_fs(struct f2fs_sb_info *);
void f2fs_balance_fs_bg(struct f2fs_sb_info *);
+int f2fs_issue_flush(struct f2fs_sb_info *);
void invalidate_blocks(struct f2fs_sb_info *, block_t);
void refresh_sit_entry(struct f2fs_sb_info *, block_t, block_t);
void clear_prefree_segments(struct f2fs_sb_info *);
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 6ba2668..302d552 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -186,7 +186,7 @@ int f2fs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
ret = wait_on_node_pages_writeback(sbi, inode->i_ino);
if (ret)
goto out;
- ret = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
+ ret = f2fs_issue_flush(F2FS_SB(inode->i_sb));
}
out:
trace_f2fs_sync_file_exit(inode, need_cp, datasync, ret);
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index f799c6a..2993624 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -13,6 +13,7 @@
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/prefetch.h>
+#include <linux/kthread.h>
#include <linux/vmalloc.h>
#include <linux/swap.h>
@@ -24,6 +25,7 @@
#define __reverse_ffz(x) __reverse_ffs(~(x))
static struct kmem_cache *discard_entry_slab;
+static struct kmem_cache *flush_cmd_slab;
/*
* __reverse_ffs is copied from include/asm-generic/bitops/__ffs.h since
@@ -195,6 +197,73 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi)
f2fs_sync_fs(sbi->sb, true);
}
+static int issue_flush_thread(void *data)
+{
+ struct f2fs_sb_info *sbi = data;
+ struct f2fs_sm_info *sm_i = SM_I(sbi);
+ wait_queue_head_t *q = &sm_i->flush_wait_queue;
+repeat:
+ spin_lock(&sm_i->issue_lock);
+ if (sm_i->issue_list) {
+ sm_i->dispatch_list = sm_i->issue_list;
+ sm_i->issue_list = sm_i->issue_tail = NULL;
+ }
+ spin_unlock(&sm_i->issue_lock);
+
+ if (sm_i->dispatch_list) {
+ struct bio *bio = bio_alloc(GFP_NOIO, 0);
+ struct flush_cmd *cmd, *next;
+ int ret;
+
+ bio->bi_bdev = sbi->sb->s_bdev;
+ ret = submit_bio_wait(WRITE_FLUSH, bio);
+
+ for (cmd = sm_i->dispatch_list; cmd; cmd = next) {
+ cmd->ret = ret;
+ next = cmd->next;
+ complete(&cmd->wait);
+ }
+ sm_i->dispatch_list = NULL;
+ }
+
+ if (kthread_should_stop())
+ return 0;
+
+ wait_event_interruptible(*q, kthread_should_stop() || sm_i->issue_list);
+ goto repeat;
+}
+
+int f2fs_issue_flush(struct f2fs_sb_info *sbi)
+{
+ struct f2fs_sm_info *sm_i = SM_I(sbi);
+ struct flush_cmd *cmd;
+ int ret;
+
+ if (!test_opt(sbi, FLUSH_MERGE))
+ return blkdev_issue_flush(sbi->sb->s_bdev, GFP_KERNEL, NULL);
+
+ cmd = f2fs_kmem_cache_alloc(flush_cmd_slab, GFP_ATOMIC);
+ cmd->next = NULL;
+ cmd->ret = 0;
+ init_completion(&cmd->wait);
+
+ spin_lock(&sm_i->issue_lock);
+ if (sm_i->issue_list)
+ sm_i->issue_tail->next = cmd;
+ else
+ sm_i->issue_list = cmd;
+ sm_i->issue_tail = cmd;
+ spin_unlock(&sm_i->issue_lock);
+
+ if (!sm_i->dispatch_list)
+ wake_up(&sm_i->flush_wait_queue);
+
+ wait_for_completion(&cmd->wait);
+ ret = cmd->ret;
+ kmem_cache_free(flush_cmd_slab, cmd);
+ return ret;
+}
+
static void __locate_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno,
enum dirty_type dirty_type)
{
@@ -1763,6 +1832,7 @@ int build_segment_manager(struct f2fs_sb_info *sbi)
{
struct f2fs_super_block *raw_super = F2FS_RAW_SUPER(sbi);
struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
+ dev_t dev = sbi->sb->s_bdev->bd_dev;
struct f2fs_sm_info *sm_info;
int err;
@@ -1790,6 +1860,15 @@ int build_segment_manager(struct f2fs_sb_info *sbi)
sm_info->nr_discards = 0;
sm_info->max_discards = 0;
+ spin_lock_init(&sm_info->issue_lock);
+
+ sm_info->f2fs_issue_flush = kthread_run(issue_flush_thread, sbi,
+ "f2fs_issue_flush-%u:%u", MAJOR(dev), MINOR(dev));
+ if (IS_ERR(sm_info->f2fs_issue_flush))
+ return PTR_ERR(sm_info->f2fs_issue_flush);
+
+ init_waitqueue_head(&sm_info->flush_wait_queue);
+
err = build_sit_info(sbi);
if (err)
return err;
@@ -1898,6 +1977,7 @@ void destroy_segment_manager(struct f2fs_sb_info *sbi)
struct f2fs_sm_info *sm_info = SM_I(sbi);
if (!sm_info)
return;
+ kthread_stop(sm_info->f2fs_issue_flush);
destroy_dirty_segmap(sbi);
destroy_curseg(sbi);
destroy_free_segmap(sbi);
@@ -1912,10 +1992,17 @@ int __init create_segment_manager_caches(void)
sizeof(struct discard_entry));
if (!discard_entry_slab)
return -ENOMEM;
+ flush_cmd_slab = f2fs_kmem_cache_create("flush_command",
+ sizeof(struct flush_cmd));
+ if (!flush_cmd_slab) {
+ kmem_cache_destroy(discard_entry_slab);
+ return -ENOMEM;
+ }
return 0;
}
void destroy_segment_manager_caches(void)
{
kmem_cache_destroy(discard_entry_slab);
+ kmem_cache_destroy(flush_cmd_slab);
}
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 9598340..d31b767 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -51,6 +51,7 @@ enum {
Opt_disable_ext_identify,
Opt_inline_xattr,
Opt_inline_data,
+ Opt_flush_merge,
Opt_err,
};
@@ -67,6 +68,7 @@ static match_table_t f2fs_tokens = {
{Opt_disable_ext_identify, "disable_ext_identify"},
{Opt_inline_xattr, "inline_xattr"},
{Opt_inline_data, "inline_data"},
+ {Opt_flush_merge, "flush_merge"},
{Opt_err, NULL},
};
@@ -334,6 +336,9 @@ static int parse_options(struct super_block *sb, char *options)
case Opt_inline_data:
set_opt(sbi, INLINE_DATA);
break;
+ case Opt_flush_merge:
+ set_opt(sbi, FLUSH_MERGE);
+ break;
default:
f2fs_msg(sb, KERN_ERR,
"Unrecognized mount option \"%s\" or missing value",
@@ -537,6 +542,8 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
seq_puts(seq, ",disable_ext_identify");
if (test_opt(sbi, INLINE_DATA))
seq_puts(seq, ",inline_data");
+ if (test_opt(sbi, FLUSH_MERGE))
+ seq_puts(seq, ",flush_merge");
seq_printf(seq, ",active_logs=%u", sbi->active_logs);
return 0;
--
1.8.4.474.g128a96c
--
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