Messages in this thread | | | Subject | Re: [PATCH] f2fs: split discard command in prior to block layer | From | Chao Yu <> | Date | Sat, 7 Jul 2018 09:39:47 +0800 |
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On 2018/7/7 9:08, Jaegeuk Kim wrote: > 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.
Let me try to refactor the patch.
Thanks,
> >> >> 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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