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Message-ID: <20180715012700.GA11571@jaegeuk-macbookpro.roam.corp.google.com>
Date: Sun, 15 Jul 2018 10:27:00 +0900
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Chao Yu <chao@...nel.org>
Cc: linux-f2fs-devel@...ts.sourceforge.net,
linux-kernel@...r.kernel.org, Chao Yu <yuchao0@...wei.com>
Subject: Re: [PATCH v2] f2fs: split discard command in prior to block layer
On 07/08, Chao Yu wrote:
> From: Chao Yu <yuchao0@...wei.com>
>
> Some devices has small max_{hw,}discard_sectors, so that in
> __blkdev_issue_discard(), one big size discard bio can be split
> into multiple small size discard bios, result in heavy load in IO
> scheduler and device, which can hang other sync IO for long time.
>
> Now, f2fs is trying to control discard commands more elaboratively,
> in order to make less conflict in between discard IO and user IO
> to enhance application's performance, so in this patch, we will
> split discard bio in f2fs in prior to in block layer to reduce
> issuing multiple discard bios in a short time.
Can we just change __submit_discard_cmd() to submit the large candidate
partially and adjust lstart in the original candidate?
>
> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> ---
> v2:
> - change to split discard command entry before submission.
> fs/f2fs/f2fs.h | 13 +++---
> fs/f2fs/segment.c | 117 +++++++++++++++++++++++++++++++++++++-----------------
> 2 files changed, 86 insertions(+), 44 deletions(-)
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index c48b655d5d8d..359526d88d3f 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -178,7 +178,6 @@ enum {
>
> #define MAX_DISCARD_BLOCKS(sbi) BLKS_PER_SEC(sbi)
> #define DEF_MAX_DISCARD_REQUEST 8 /* issue 8 discards per round */
> -#define DEF_MAX_DISCARD_LEN 512 /* Max. 2MB per discard */
> #define DEF_MIN_DISCARD_ISSUE_TIME 50 /* 50 ms, if exists */
> #define DEF_MID_DISCARD_ISSUE_TIME 500 /* 500 ms, if device busy */
> #define DEF_MAX_DISCARD_ISSUE_TIME 60000 /* 60 s, if no candidates */
> @@ -709,22 +708,22 @@ static inline void set_extent_info(struct extent_info *ei, unsigned int fofs,
> }
>
> static inline bool __is_discard_mergeable(struct discard_info *back,
> - struct discard_info *front)
> + struct discard_info *front, unsigned int max_len)
> {
> return (back->lstart + back->len == front->lstart) &&
> - (back->len + front->len < DEF_MAX_DISCARD_LEN);
> + (back->len + front->len <= max_len);
> }
>
> static inline bool __is_discard_back_mergeable(struct discard_info *cur,
> - struct discard_info *back)
> + struct discard_info *back, unsigned int max_len)
> {
> - return __is_discard_mergeable(back, cur);
> + return __is_discard_mergeable(back, cur, max_len);
> }
>
> static inline bool __is_discard_front_mergeable(struct discard_info *cur,
> - struct discard_info *front)
> + struct discard_info *front, unsigned int max_len)
> {
> - return __is_discard_mergeable(cur, front);
> + return __is_discard_mergeable(cur, front, max_len);
> }
>
> static inline bool __is_extent_mergeable(struct extent_info *back,
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index f7f56dd091b4..cbf8f3f9a8e7 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -966,17 +966,24 @@ static void __init_discard_policy(struct f2fs_sb_info *sbi,
> }
> }
>
> -
> +static void __update_discard_tree_range(struct f2fs_sb_info *sbi,
> + struct block_device *bdev, block_t lstart,
> + block_t start, block_t len);
> /* this function is copied from blkdev_issue_discard from block/blk-lib.c */
> static void __submit_discard_cmd(struct f2fs_sb_info *sbi,
> struct discard_policy *dpolicy,
> - struct discard_cmd *dc)
> + struct discard_cmd *dc,
> + unsigned int *issued)
> {
> + struct block_device *bdev = dc->bdev;
> + struct request_queue *q = bdev_get_queue(bdev);
> + unsigned int max_discard_blocks =
> + SECTOR_TO_BLOCK(q->limits.max_discard_sectors);
> struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> struct list_head *wait_list = (dpolicy->type == DPOLICY_FSTRIM) ?
> &(dcc->fstrim_list) : &(dcc->wait_list);
> - struct bio *bio = NULL;
> int flag = dpolicy->sync ? REQ_SYNC : 0;
> + block_t lstart, start, len, total_len;
>
> if (dc->state != D_PREP)
> return;
> @@ -984,30 +991,63 @@ static void __submit_discard_cmd(struct f2fs_sb_info *sbi,
> if (is_sbi_flag_set(sbi, SBI_NEED_FSCK))
> return;
>
> - trace_f2fs_issue_discard(dc->bdev, dc->start, dc->len);
> -
> - dc->error = __blkdev_issue_discard(dc->bdev,
> - SECTOR_FROM_BLOCK(dc->start),
> - SECTOR_FROM_BLOCK(dc->len),
> - GFP_NOFS, 0, &bio);
> - if (!dc->error) {
> - /* should keep before submission to avoid D_DONE right away */
> - dc->state = D_SUBMIT;
> - atomic_inc(&dcc->issued_discard);
> - atomic_inc(&dcc->issing_discard);
> - if (bio) {
> - bio->bi_private = dc;
> - bio->bi_end_io = f2fs_submit_discard_endio;
> - bio->bi_opf |= flag;
> - submit_bio(bio);
> - list_move_tail(&dc->list, wait_list);
> - __check_sit_bitmap(sbi, dc->start, dc->start + dc->len);
> -
> - f2fs_update_iostat(sbi, FS_DISCARD, 1);
> + trace_f2fs_issue_discard(bdev, dc->start, dc->len);
> +
> + lstart = dc->lstart;
> + start = dc->start;
> + len = dc->len;
> + total_len = len;
> +
> + while (total_len && *issued < dpolicy->max_requests) {
> + struct bio *bio = NULL;
> +
> + if (len > max_discard_blocks)
> + len = max_discard_blocks;
> +
> + dc->error = __blkdev_issue_discard(bdev,
> + SECTOR_FROM_BLOCK(start),
> + SECTOR_FROM_BLOCK(len),
> + GFP_NOFS, 0, &bio);
> + if (!dc->error) {
> + /*
> + * should keep before submission to avoid D_DONE
> + * right away
> + */
> + dc->state = D_SUBMIT;
> + dc->len = len;
> + atomic_inc(&dcc->issued_discard);
> + atomic_inc(&dcc->issing_discard);
> + if (bio) {
> + bio->bi_private = dc;
> + bio->bi_end_io = f2fs_submit_discard_endio;
> + bio->bi_opf |= flag;
> + submit_bio(bio);
> + list_move_tail(&dc->list, wait_list);
> + __check_sit_bitmap(sbi, dc->start,
> + dc->start + dc->len);
> +
> + f2fs_update_iostat(sbi, FS_DISCARD, 1);
> + }
> + } else {
> + __remove_discard_cmd(sbi, dc);
> + return;
> + }
> + lstart += len;
> + start += len;
> + total_len -= len;
> + len = total_len;
> + (*issued)++;
> +
> + if (len) {
> + __update_discard_tree_range(sbi, bdev, lstart,
> + start, len);
> + dc = (struct discard_cmd *)f2fs_lookup_rb_tree(
> + &dcc->root, NULL, lstart);
> + f2fs_bug_on(sbi, !dc);
> }
> - } else {
> - __remove_discard_cmd(sbi, dc);
> }
> +
> + return;
> }
>
> static struct discard_cmd *__insert_discard_tree(struct f2fs_sb_info *sbi,
> @@ -1088,10 +1128,11 @@ static void __update_discard_tree_range(struct f2fs_sb_info *sbi,
> struct discard_cmd *dc;
> struct discard_info di = {0};
> struct rb_node **insert_p = NULL, *insert_parent = NULL;
> + struct request_queue *q = bdev_get_queue(bdev);
> + unsigned int max_discard_blocks =
> + SECTOR_TO_BLOCK(q->limits.max_discard_sectors);
> block_t end = lstart + len;
>
> - mutex_lock(&dcc->cmd_lock);
> -
> dc = (struct discard_cmd *)f2fs_lookup_rb_tree_ret(&dcc->root,
> NULL, lstart,
> (struct rb_entry **)&prev_dc,
> @@ -1131,7 +1172,8 @@ static void __update_discard_tree_range(struct f2fs_sb_info *sbi,
>
> if (prev_dc && prev_dc->state == D_PREP &&
> prev_dc->bdev == bdev &&
> - __is_discard_back_mergeable(&di, &prev_dc->di)) {
> + __is_discard_back_mergeable(&di, &prev_dc->di,
> + max_discard_blocks)) {
> prev_dc->di.len += di.len;
> dcc->undiscard_blks += di.len;
> __relocate_discard_cmd(dcc, prev_dc);
> @@ -1142,7 +1184,8 @@ static void __update_discard_tree_range(struct f2fs_sb_info *sbi,
>
> if (next_dc && next_dc->state == D_PREP &&
> next_dc->bdev == bdev &&
> - __is_discard_front_mergeable(&di, &next_dc->di)) {
> + __is_discard_front_mergeable(&di, &next_dc->di,
> + max_discard_blocks)) {
> next_dc->di.lstart = di.lstart;
> next_dc->di.len += di.len;
> next_dc->di.start = di.start;
> @@ -1165,8 +1208,6 @@ static void __update_discard_tree_range(struct f2fs_sb_info *sbi,
> node = rb_next(&prev_dc->rb_node);
> next_dc = rb_entry_safe(node, struct discard_cmd, rb_node);
> }
> -
> - mutex_unlock(&dcc->cmd_lock);
> }
>
> static int __queue_discard_cmd(struct f2fs_sb_info *sbi,
> @@ -1181,7 +1222,9 @@ static int __queue_discard_cmd(struct f2fs_sb_info *sbi,
>
> blkstart -= FDEV(devi).start_blk;
> }
> + mutex_lock(&SM_I(sbi)->dcc_info->cmd_lock);
> __update_discard_tree_range(sbi, bdev, lblkstart, blkstart, blklen);
> + mutex_unlock(&SM_I(sbi)->dcc_info->cmd_lock);
> return 0;
> }
>
> @@ -1220,9 +1263,9 @@ static unsigned int __issue_discard_cmd_orderly(struct f2fs_sb_info *sbi,
> }
>
> dcc->next_pos = dc->lstart + dc->len;
> - __submit_discard_cmd(sbi, dpolicy, dc);
> + __submit_discard_cmd(sbi, dpolicy, dc, &issued);
>
> - if (++issued >= dpolicy->max_requests)
> + if (issued >= dpolicy->max_requests)
> break;
> next:
> node = rb_next(&dc->rb_node);
> @@ -1277,9 +1320,9 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
> break;
> }
>
> - __submit_discard_cmd(sbi, dpolicy, dc);
> + __submit_discard_cmd(sbi, dpolicy, dc, &issued);
>
> - if (++issued >= dpolicy->max_requests)
> + if (issued >= dpolicy->max_requests)
> break;
> }
> blk_finish_plug(&plug);
> @@ -2475,9 +2518,9 @@ static unsigned int __issue_discard_cmd_range(struct f2fs_sb_info *sbi,
> goto skip;
> }
>
> - __submit_discard_cmd(sbi, dpolicy, dc);
> + __submit_discard_cmd(sbi, dpolicy, dc, &issued);
>
> - if (++issued >= dpolicy->max_requests) {
> + if (issued >= dpolicy->max_requests) {
> start = dc->lstart + dc->len;
>
> blk_finish_plug(&plug);
> --
> 2.16.2.17.g38e79b1fd
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