Messages in this thread | | | Subject | Re: [f2fs-dev] [PATCH v2] f2fs: split discard command in prior to block layer | From | Chao Yu <> | Date | Mon, 23 Jul 2018 21:22:14 +0800 |
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On 2018/7/23 20:47, Jaegeuk Kim wrote: > 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?
Got you, let me try to refactor a bit for that.
Thanks,
> > 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 > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel >
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