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SubjectRe: [f2fs-dev] [PATCH v5] f2fs: fix performance issue observed with multi-thread sequential read
This reverts the commit - "b93f771 - f2fs: remove writepages lock"
to fix the drop in sequential read throughput.

Test: ./tiotest -t 32 -d /data/tio_tmp -f 32 -b 524288 -k 1 -k 3 -L
device: UFS

Before -
read throughput: 185 MB/s
total read requests: 85177 (of these ~80000 are 4KB size requests).
total write requests: 2546 (of these ~2208 requests are written in 512KB).

After -
read throughput: 758 MB/s
total read requests: 2417 (of these ~2042 are 512KB reads).
total write requests: 2701 (of these ~2034 requests are written in 512KB).

Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
Change log from v4:
- add __should_serialize_io
- fix wrong condition

Documentation/ABI/testing/sysfs-fs-f2fs | 8 ++++++++
fs/f2fs/data.c | 21 +++++++++++++++++++++
fs/f2fs/f2fs.h | 2 ++
fs/f2fs/segment.c | 1 +
fs/f2fs/super.c | 1 +
fs/f2fs/sysfs.c | 2 ++
6 files changed, 35 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
index 9b0123388f18..94a24aedcdb2 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -51,6 +51,14 @@ Description:
Controls the dirty page count condition for the in-place-update
policies.

+What: /sys/fs/f2fs/<disk>/min_seq_blocks
+Date: August 2018
+Contact: "Jaegeuk Kim" <jaegeuk@kernel.org>
+Description:
+ Controls the dirty page count condition for batched sequential
+ writes in ->writepages.
+
+
What: /sys/fs/f2fs/<disk>/min_hot_blocks
Date: March 2017
Contact: "Jaegeuk Kim" <jaegeuk@kernel.org>
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 43d3723dc886..bdcb023506a7 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2122,6 +2122,18 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
return ret;
}

+static inline bool __should_serialize_io(struct inode *inode,
+ struct writeback_control *wbc)
+{
+ if (!S_ISREG(inode->i_mode))
+ return false;
+ if (wbc->sync_mode != WB_SYNC_ALL)
+ return true;
+ if (get_dirty_pages(inode) >= SM_I(F2FS_I_SB(inode))->min_seq_blocks)
+ return true;
+ return false;
+}
+
static int __f2fs_write_data_pages(struct address_space *mapping,
struct writeback_control *wbc,
enum iostat_type io_type)
@@ -2130,6 +2142,7 @@ static int __f2fs_write_data_pages(struct address_space *mapping,
struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
struct blk_plug plug;
int ret;
+ bool locked = false;

/* deal with chardevs and other special file */
if (!mapping->a_ops->writepage)
@@ -2160,10 +2173,18 @@ static int __f2fs_write_data_pages(struct address_space *mapping,
else if (atomic_read(&sbi->wb_sync_req[DATA]))
goto skip_write;

+ if (__should_serialize_io(inode, wbc)) {
+ mutex_lock(&sbi->writepages);
+ locked = true;
+ }
+
blk_start_plug(&plug);
ret = f2fs_write_cache_pages(mapping, wbc, io_type);
blk_finish_plug(&plug);

+ if (locked)
+ mutex_unlock(&sbi->writepages);
+
if (wbc->sync_mode == WB_SYNC_ALL)
atomic_dec(&sbi->wb_sync_req[DATA]);
/*
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 9a6ba4a8d338..170573f8a04a 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -913,6 +913,7 @@ struct f2fs_sm_info {
unsigned int ipu_policy; /* in-place-update policy */
unsigned int min_ipu_util; /* in-place-update threshold */
unsigned int min_fsync_blocks; /* threshold for fsync */
+ unsigned int min_seq_blocks; /* threshold for sequential blocks */
unsigned int min_hot_blocks; /* threshold for hot block allocation */
unsigned int min_ssr_sections; /* threshold to trigger SSR allocation */

@@ -1133,6 +1134,7 @@ struct f2fs_sb_info {
struct rw_semaphore sb_lock; /* lock for raw super block */
int valid_super_block; /* valid super block no */
unsigned long s_flag; /* flags for sbi */
+ struct mutex writepages; /* mutex for writepages() */

#ifdef CONFIG_BLK_DEV_ZONED
unsigned int blocks_per_blkz; /* F2FS blocks per zone */
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index b136e39e1e9e..20650e25117b 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -4127,6 +4127,7 @@ int f2fs_build_segment_manager(struct f2fs_sb_info *sbi)
sm_info->ipu_policy = 1 << F2FS_IPU_FSYNC;
sm_info->min_ipu_util = DEF_MIN_IPU_UTIL;
sm_info->min_fsync_blocks = DEF_MIN_FSYNC_BLOCKS;
+ sm_info->min_seq_blocks = sbi->blocks_per_seg * sbi->segs_per_sec;
sm_info->min_hot_blocks = DEF_MIN_HOT_BLOCKS;
sm_info->min_ssr_sections = reserved_sections(sbi);

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index be41dbd7b261..53d70b64fea1 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -2842,6 +2842,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
/* init f2fs-specific super block info */
sbi->valid_super_block = valid_super_block;
mutex_init(&sbi->gc_mutex);
+ mutex_init(&sbi->writepages);
mutex_init(&sbi->cp_mutex);
init_rwsem(&sbi->node_write);
init_rwsem(&sbi->node_change);
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index cd2e030e47b8..81c0e5337443 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -397,6 +397,7 @@ F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_ipu_util, min_ipu_util);
F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_fsync_blocks, min_fsync_blocks);
+F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_seq_blocks, min_seq_blocks);
F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_hot_blocks, min_hot_blocks);
F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_ssr_sections, min_ssr_sections);
F2FS_RW_ATTR(NM_INFO, f2fs_nm_info, ram_thresh, ram_thresh);
@@ -449,6 +450,7 @@ static struct attribute *f2fs_attrs[] = {
ATTR_LIST(ipu_policy),
ATTR_LIST(min_ipu_util),
ATTR_LIST(min_fsync_blocks),
+ ATTR_LIST(min_seq_blocks),
ATTR_LIST(min_hot_blocks),
ATTR_LIST(min_ssr_sections),
ATTR_LIST(max_victim_search),
--
2.17.0.441.gb46fe60e1d-goog
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