[PATCH v4] f2fs: introduce discard_granularity sysfs entry
From: Chao Yu
Date: Mon Aug 07 2017 - 11:12:31 EST
From: Chao Yu <yuchao0@xxxxxxxxxx>
Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables
f2fs to issue 4K size discard in real-time discard mode. However, issuing
smaller discard may cost more lifetime but releasing less free space in
flash device. Since f2fs has ability of separating hot/cold data and
garbage collection, we can expect that small-sized invalid region would
expand soon with OPU, deletion or garbage collection on valid datas, so
it's better to delay or skip issuing smaller size discards, it could help
to reduce overmuch consumption of IO bandwidth and lifetime of flash
storage.
This patch makes f2fs selectng 64K size as its default minimal
granularity, and issue discard with the size which is not smaller than
minimal granularity. Also it exposes discard granularity as sysfs entry
for configuration in different scenario.
Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
---
v4: minor change in commit log.
Documentation/ABI/testing/sysfs-fs-f2fs | 9 +++++++++
fs/f2fs/f2fs.h | 4 ++++
fs/f2fs/segment.c | 23 ++++++++++++++++++++++-
fs/f2fs/sysfs.c | 7 +++++++
4 files changed, 42 insertions(+), 1 deletion(-)
diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
index 84c606fb3ca4..c579ce5e0ef5 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -57,6 +57,15 @@ Contact: "Jaegeuk Kim" <jaegeuk.kim@xxxxxxxxxxx>
Description:
Controls the issue rate of small discard commands.
+What: /sys/fs/f2fs/<disk>/discard_granularity
+Date: July 2017
+Contact: "Chao Yu" <yuchao0@xxxxxxxxxx>
+Description:
+ Controls discard granularity of inner discard thread, inner thread
+ will not issue discards with size that is smaller than granularity.
+ The unit size is one block, now only support configuring in range
+ of [1, 512].
+
What: /sys/fs/f2fs/<disk>/max_victim_search
Date: January 2014
Contact: "Jaegeuk Kim" <jaegeuk.kim@xxxxxxxxxxx>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 0ccccbfdeeab..1bcaa93bfed7 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -195,6 +195,9 @@ struct discard_entry {
unsigned char discard_map[SIT_VBLOCK_MAP_SIZE]; /* segment discard bitmap */
};
+/* default discard granularity of inner discard thread, unit: block count */
+#define DEFAULT_DISCARD_GRANULARITY 16
+
/* max discard pend list number */
#define MAX_PLIST_NUM 512
#define plist_idx(blk_num) ((blk_num) >= MAX_PLIST_NUM ? \
@@ -240,6 +243,7 @@ struct discard_cmd_control {
struct mutex cmd_lock;
unsigned int nr_discards; /* # of discards in the list */
unsigned int max_discards; /* max. discards to be issued */
+ unsigned int discard_granularity; /* discard granularity */
unsigned int undiscard_blks; /* # of undiscard blocks */
atomic_t issued_discard; /* # of issued discard */
atomic_t issing_discard; /* # of issing discard */
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 71c2e0ac13d7..f336f8c541f0 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1019,7 +1019,8 @@ static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
f2fs_bug_on(sbi,
!__check_rb_tree_consistence(sbi, &dcc->root));
blk_start_plug(&plug);
- for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
+ for (i = MAX_PLIST_NUM - 1; i >= 0 &&
+ i >= dcc->discard_granularity - 1; i--) {
pend_list = &dcc->pend_list[i];
list_for_each_entry_safe(dc, tmp, pend_list, list) {
f2fs_bug_on(sbi, dc->state != D_PREP);
@@ -1035,6 +1036,24 @@ static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
mutex_unlock(&dcc->cmd_lock);
}
+static void __drop_discard_cmd(struct f2fs_sb_info *sbi)
+{
+ struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+ struct list_head *pend_list;
+ struct discard_cmd *dc, *tmp;
+ int i;
+
+ mutex_lock(&dcc->cmd_lock);
+ for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
+ pend_list = &dcc->pend_list[i];
+ list_for_each_entry_safe(dc, tmp, pend_list, list) {
+ f2fs_bug_on(sbi, dc->state != D_PREP);
+ __remove_discard_cmd(sbi, dc);
+ }
+ }
+ mutex_unlock(&dcc->cmd_lock);
+}
+
static void __wait_one_discard_bio(struct f2fs_sb_info *sbi,
struct discard_cmd *dc)
{
@@ -1117,6 +1136,7 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
{
__issue_discard_cmd(sbi, false);
+ __drop_discard_cmd(sbi);
__wait_discard_cmd(sbi, false);
}
@@ -1449,6 +1469,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
atomic_set(&dcc->discard_cmd_cnt, 0);
dcc->nr_discards = 0;
dcc->max_discards = MAIN_SEGS(sbi) << sbi->log_blocks_per_seg;
+ dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
dcc->undiscard_blks = 0;
dcc->root = RB_ROOT;
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 045b948c7466..4e5a95e9e666 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -152,6 +152,11 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
spin_unlock(&sbi->stat_lock);
return count;
}
+
+ if (!strcmp(a->attr.name, "discard_granularity") &&
+ (t == 0 || t > MAX_PLIST_NUM))
+ return -EINVAL;
+
*ui = t;
if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
@@ -241,6 +246,7 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_no_gc_sleep_time, no_gc_sleep_time);
F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, max_discards);
+F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, reserved_blocks);
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);
@@ -281,6 +287,7 @@ static struct attribute *f2fs_attrs[] = {
ATTR_LIST(gc_idle),
ATTR_LIST(reclaim_segments),
ATTR_LIST(max_small_discards),
+ ATTR_LIST(discard_granularity),
ATTR_LIST(batched_trim_sections),
ATTR_LIST(ipu_policy),
ATTR_LIST(min_ipu_util),
--
2.14.0