[PATCH v2] f2fs: introduce discard_granularity sysfs entry
From: Chao Yu
Date: Wed Aug 02 2017 - 11:16:23 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 flash lifetime but release less free
space in storage. Since f2fs has ability of separating hot/cold data and
garbage collection, we can expect that size of small invalid region may
expand with data ipu/deletion or garbage collection, so it's better to
delay or skip issuing smaller size discard, it could help to reduce
overmuch consumption of IO bandwidth and lifetime of flash storage.
This patch makes f2fs issuing discard with granularity of 64K by default,
and exposes discard granularity as sysfs entry for configuration in
different scenario.
Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
---
v2:
- limit lower boundary to one block size.
- drop discard cmds in put_super.
Documentation/ABI/testing/sysfs-fs-f2fs | 7 +++++++
fs/f2fs/f2fs.h | 4 ++++
fs/f2fs/segment.c | 23 +++++++++++++++++++++++
fs/f2fs/sysfs.c | 6 ++++++
4 files changed, 40 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
index 84c606fb3ca4..964aaefafc72 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -57,6 +57,13 @@ 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, discard thread
+ will not issue discards with size that is smaller than granularity.
+
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 5aedd609cceb..547bd9d0527d 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -194,6 +194,9 @@ 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 ? \
@@ -239,6 +242,7 @@ 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 2a5672a20a62..2d533f79bf26 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1017,6 +1017,9 @@ static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
!__check_rb_tree_consistence(sbi, &dcc->root));
blk_start_plug(&plug);
for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
+ if (i < dcc->discard_granularity - 1)
+ break;
+
pend_list = &dcc->pend_list[i];
list_for_each_entry_safe(dc, tmp, pend_list, list) {
f2fs_bug_on(sbi, dc->state != D_PREP);
@@ -1032,6 +1035,24 @@ 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 = 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);
+ __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)
{
@@ -1114,6 +1135,7 @@ 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);
}
@@ -1446,6 +1468,7 @@ 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 5a78b9af92ef..fe5829486500 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -124,6 +124,10 @@ 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)
+ return -EINVAL;
+
*ui = t;
return count;
}
@@ -178,6 +182,7 @@ 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);
@@ -205,6 +210,7 @@ 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),
--
2.13.0.90.g1eb437020