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Date: Sun, 15 Jul 2018 12:13:08 +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 07/15, Chao Yu wrote:
> Hi Jaegeuk,
>
> On 2018/7/15 9:27, Jaegeuk Kim wrote:
> > 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?
>
> Yep, could you check __submit_discard_cmd() implementation below? Does that
> match the thoughts from you?
>
> Thanks,
>
> >
> >>
> >> 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,
> >> }
> >> }
> >>
> >> -
===================== BEGIN
> >> +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);
Keep the original one, since it's partially failed?
> >> + return;
> >> + }
> >> + lstart += len;
> >> + start += len;
> >> + total_len -= len;
> >> + len = total_len;
> >> + (*issued)++;
> >> +
> >> + if (len) {
> >> + __update_discard_tree_range(sbi, bdev, lstart,
> >> + start, len);
Do we really need this? We already grabbed one candidate which was not merged
well.
> >> + dc = (struct discard_cmd *)f2fs_lookup_rb_tree(
> >> + &dcc->root, NULL, lstart);
> >> + f2fs_bug_on(sbi, !dc);
> >> }
> >> - } else {
> >> - __remove_discard_cmd(sbi, dc);
> >> }
> >> +
> >> + return;
> >> }
======================= END
> >>
> >> 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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