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Subject[PATCH v2 2/6] f2fs: wrap discard policy
Date
From: Chao Yu <yuchao0@huawei.com>

This patch wraps scattered optional parameters into discard policy as
below, later, with it we expect that we can adjust these parameters with
proper strategy in different scenario.

struct discard_policy {
unsigned int min_interval; /* used for candidates exist */
unsigned int max_interval; /* used for candidates not exist */
unsigned int max_requests; /* # of discards issued per round */
unsigned int io_aware_gran; /* minimum granularity discard not be aware of I/O */
bool io_aware; /* issue discard in idle time */
bool sync; /* submit discard with REQ_SYNC flag */
};

This patch doesn't change any logic of codes.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
v2:
- rebase on last codes of Jaegeuk's dev-test branch.
fs/f2fs/f2fs.h | 12 +++++++++++-
fs/f2fs/segment.c | 38 +++++++++++++++++++++++++++++---------
2 files changed, 40 insertions(+), 10 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 6d51e8342513..67dd6a317384 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -149,7 +149,7 @@ enum {
#define BATCHED_TRIM_BLOCKS(sbi) \
(BATCHED_TRIM_SEGMENTS(sbi) << (sbi)->log_blocks_per_seg)
#define MAX_DISCARD_BLOCKS(sbi) BLKS_PER_SEC(sbi)
-#define DISCARD_ISSUE_RATE 8
+#define DEF_MAX_DISCARD_REQUEST 8 /* issue 8 discards per round */
#define DEF_MIN_DISCARD_ISSUE_TIME 50 /* 50 ms, if exists */
#define DEF_MAX_DISCARD_ISSUE_TIME 60000 /* 60 s, if no candidates */
#define DEF_CP_INTERVAL 60 /* 60 secs */
@@ -245,6 +245,15 @@ struct discard_cmd {
int error; /* bio error */
};

+struct discard_policy {
+ unsigned int min_interval; /* used for candidates exist */
+ unsigned int max_interval; /* used for candidates not exist */
+ unsigned int max_requests; /* # of discards issued per round */
+ unsigned int io_aware_gran; /* minimum granularity discard not be aware of I/O */
+ bool io_aware; /* issue discard in idle time */
+ bool sync; /* submit discard with REQ_SYNC flag */
+};
+
struct discard_cmd_control {
struct task_struct *f2fs_issue_discard; /* discard thread */
struct list_head entry_list; /* 4KB discard entry list */
@@ -263,6 +272,7 @@ struct discard_cmd_control {
atomic_t issing_discard; /* # of issing discard */
atomic_t discard_cmd_cnt; /* # of cached cmd count */
struct rb_root root; /* root of discard rb-tree */
+ struct discard_policy dpolicy; /* current discard policy */
};

/* for the list of fsync inodes, used only during recovery */
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index a0a0a887fc31..5853187230e7 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -879,6 +879,7 @@ static void __submit_discard_cmd(struct f2fs_sb_info *sbi,
struct list_head *wait_list = fstrim ? &(dcc->fstrim_list) :
&(dcc->wait_list);
struct bio *bio = NULL;
+ int flag = dcc->dpolicy.sync ? REQ_SYNC : 0;

if (dc->state != D_PREP)
return;
@@ -897,7 +898,7 @@ static void __submit_discard_cmd(struct f2fs_sb_info *sbi,
if (bio) {
bio->bi_private = dc;
bio->bi_end_io = f2fs_submit_discard_endio;
- bio->bi_opf |= REQ_SYNC;
+ bio->bi_opf |= flag;
submit_bio(bio);
list_move_tail(&dc->list, wait_list);
__check_sit_bitmap(sbi, dc->start, dc->start + dc->len);
@@ -1092,6 +1093,7 @@ static void __issue_discard_cmd_range(struct f2fs_sb_info *sbi,
struct discard_cmd *prev_dc = NULL, *next_dc = NULL;
struct rb_node **insert_p = NULL, *insert_parent = NULL;
struct discard_cmd *dc;
+ struct discard_policy *dpolicy = &dcc->dpolicy;
struct blk_plug plug;
int issued;

@@ -1124,7 +1126,7 @@ static void __issue_discard_cmd_range(struct f2fs_sb_info *sbi,

__submit_discard_cmd(sbi, dc, true);

- if (++issued >= DISCARD_ISSUE_RATE) {
+ if (++issued >= dpolicy->max_requests) {
start = dc->lstart + dc->len;

blk_finish_plug(&plug);
@@ -1152,6 +1154,7 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
struct list_head *pend_list;
struct discard_cmd *dc, *tmp;
struct blk_plug plug;
+ struct discard_policy *dpolicy = &dcc->dpolicy;
int iter = 0, issued = 0;
int i;
bool io_interrupted = false;
@@ -1179,14 +1182,16 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
continue;
}

- if (is_idle(sbi)) {
- __submit_discard_cmd(sbi, dc, false);
- issued++;
- } else {
+ if (dpolicy->io_aware && i < dpolicy->io_aware_gran &&
+ !is_idle(sbi)) {
io_interrupted = true;
+ goto skip;
}

- if (++iter >= DISCARD_ISSUE_RATE)
+ __submit_discard_cmd(sbi, dc, false);
+ issued++;
+skip:
+ if (++iter >= dpolicy->max_requests)
goto out;
}
if (list_empty(pend_list) && dcc->pend_list_tag[i] & P_TRIM)
@@ -1335,6 +1340,7 @@ static int issue_discard_thread(void *data)
struct f2fs_sb_info *sbi = data;
struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
wait_queue_head_t *q = &dcc->discard_wait_queue;
+ struct discard_policy *dpolicy = &dcc->dpolicy;
unsigned int wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
int issued;

@@ -1361,9 +1367,9 @@ static int issue_discard_thread(void *data)
issued = __issue_discard_cmd(sbi, true);
if (issued) {
__wait_all_discard_cmd(sbi, true);
- wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
+ wait_ms = dpolicy->min_interval;
} else {
- wait_ms = DEF_MAX_DISCARD_ISSUE_TIME;
+ wait_ms = dpolicy->max_interval;
}

sb_end_intwrite(sbi->sb);
@@ -1648,6 +1654,18 @@ void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
wake_up_discard_thread(sbi, false);
}

+static void inline init_discard_policy(struct discard_cmd_control *dcc)
+{
+ struct discard_policy *dpolicy = &dcc->dpolicy;
+
+ dpolicy->min_interval = DEF_MIN_DISCARD_ISSUE_TIME;
+ dpolicy->max_interval = DEF_MAX_DISCARD_ISSUE_TIME;
+ dpolicy->max_requests = DEF_MAX_DISCARD_REQUEST;
+ dpolicy->io_aware_gran = MAX_PLIST_NUM;
+ dpolicy->io_aware = true;
+ dpolicy->sync = true;
+}
+
static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
{
dev_t dev = sbi->sb->s_bdev->bd_dev;
@@ -1681,6 +1699,8 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
dcc->undiscard_blks = 0;
dcc->root = RB_ROOT;

+ init_discard_policy(dcc);
+
init_waitqueue_head(&dcc->discard_wait_queue);
SM_I(sbi)->dcc_info = dcc;
init_thread:
--
2.14.1.145.gb3622a4ee
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