Messages in this thread | | | Date | Mon, 23 Jul 2018 21:47:47 +0900 | From | Jaegeuk Kim <> | Subject | Re: [PATCH v2] f2fs: split discard command in prior to block layer |
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On 07/15, Chao Yu wrote: > On 2018/7/15 11:13, Jaegeuk Kim wrote: > > 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@huawei.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@huawei.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? > > During __submit_discard_cmd(), we are trying to split original dc into multiple > dc, and once we failed to submit some of them, we will remove corresponding dc, > the removal logic is the same as before, not being changed... > > If we want to keep failed dc and do retry, we'd better add another patch for > that, right?
I thought removing failed portion of the dc.
> > > > >>>> + 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. > > You mean submitting multiple bios based on one large size dc?
Yes.
> > Previously, one bio references to one dc as below, in end_io, it will change > dc->state which can be detected by its own waiter. > > bio->bi_private = dc; > bio->bi_end_io = f2fs_submit_discard_endio; > bio->bi_opf |= flag; > > If multiple bios reference to one dc, it will be more complicated to handle > that. How do you think?
I was concerned about too many entries in the lists. How about adding a refcnt to count how many bios were issued on the dc?
Thanks,
> > Thanks, > > > > >>>> + 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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