Messages in this thread | | | Date | Fri, 6 Jul 2018 18:08:34 -0700 | From | Jaegeuk Kim <> | Subject | Re: [PATCH] f2fs: split discard command in prior to block layer |
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On 07/07, Chao Yu wrote: > Hi Jaegeuk, > > On 2018/7/7 6:45, Jaegeuk Kim wrote: > > On 07/04, 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. > > > > Hi Chao, > > > > In terms of # of candidates, can we control this when actually issuing > > the discard commands? > > IIUC, you mean once we pick one discard entry in rbtree, if > max_{hw,}discard_sectors is smaller than size of this discard, then we can split > it into smaller ones by discard_sectors, and just issue one or partials of them?
Yes, sort of.
> > Thanks, > > > > > Thanks, > > > >> > >> Signed-off-by: Chao Yu <yuchao0@huawei.com> > >> --- > >> fs/f2fs/f2fs.h | 13 ++++++------- > >> fs/f2fs/segment.c | 25 ++++++++++++++++++++++--- > >> 2 files changed, 28 insertions(+), 10 deletions(-) > >> > >> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > >> index a9da5a089cb4..a09d2b2d9520 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 */ > >> @@ -701,22 +700,22 @@ 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 4648561e2bfd..8e417a12684d 100644 > >> --- a/fs/f2fs/segment.c > >> +++ b/fs/f2fs/segment.c > >> @@ -1086,6 +1086,9 @@ 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); > >> @@ -1129,7 +1132,8 @@ 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); > >> @@ -1140,7 +1144,8 @@ 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; > >> @@ -1170,7 +1175,11 @@ static void __update_discard_tree_range(struct f2fs_sb_info *sbi, > >> static int __queue_discard_cmd(struct f2fs_sb_info *sbi, > >> struct block_device *bdev, block_t blkstart, block_t blklen) > >> { > >> + struct request_queue *q = bdev_get_queue(bdev); > >> + unsigned int max_discard_blocks = > >> + SECTOR_TO_BLOCK(q->limits.max_discard_sectors); > >> block_t lblkstart = blkstart; > >> + block_t total_len = blklen; > >> > >> trace_f2fs_queue_discard(bdev, blkstart, blklen); > >> > >> @@ -1179,7 +1188,17 @@ static int __queue_discard_cmd(struct f2fs_sb_info *sbi, > >> > >> blkstart -= FDEV(devi).start_blk; > >> } > >> - __update_discard_tree_range(sbi, bdev, lblkstart, blkstart, blklen); > >> + > >> + while (total_len) { > >> + if (blklen > max_discard_blocks) > >> + blklen = max_discard_blocks; > >> + __update_discard_tree_range(sbi, bdev, lblkstart, > >> + blkstart, blklen); > >> + lblkstart += blklen; > >> + blkstart += blklen; > >> + total_len -= blklen; > >> + blklen = total_len; > >> + } > >> return 0; > >> } > >> > >> -- > >> 2.16.2.17.g38e79b1fd
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