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Date: Mon, 12 Dec 2022 21:40:40 +0800
From: Chao Yu <chao@...nel.org>
To: Yangtao Li <frank.li@...o.com>, jaegeuk@...nel.org
Cc: linux-f2fs-devel@...ts.sourceforge.net,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] f2fs: add support for counting time of submit discard
cmd
On 2022/12/12 20:51, Yangtao Li wrote:
> This patch adds support for counting the average time and
> peak time of submit discard command, and we can see its
> value in debugfs.
>
> It is not sure whether the block layer has recorded these
> data, and these data are allowed to be accessed by fs,
> or they are only exported to user space.
>
> On the one hand, I added these data to better understand
> the current device operating status, and to further control
> the discard process in a more detailed manner based on the
> discard submit time in the future.
Again, w'd better to consider this functionality only when DEBUG_FS is
enabled.
>
> Signed-off-by: Yangtao Li <frank.li@...o.com>
> ---
> fs/f2fs/debug.c | 10 +++++++---
> fs/f2fs/f2fs.h | 6 ++++++
> fs/f2fs/segment.c | 21 +++++++++++++++++++--
> 3 files changed, 32 insertions(+), 5 deletions(-)
>
> diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
> index 32af4f0c5735..142c256b89d9 100644
> --- a/fs/f2fs/debug.c
> +++ b/fs/f2fs/debug.c
> @@ -120,6 +120,10 @@ static void update_general_status(struct f2fs_sb_info *sbi)
> llist_empty(&SM_I(sbi)->fcc_info->issue_list);
> }
> if (SM_I(sbi)->dcc_info) {
> + struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> +
> + si->discard_avg = dcc->discard_time_avg;
> + si->discard_peak = dcc->discard_time_peak;
> si->nr_discarded =
> atomic_read(&SM_I(sbi)->dcc_info->issued_discard);
> si->nr_discarding =
> @@ -545,9 +549,9 @@ static int stat_show(struct seq_file *s, void *v)
> si->nr_wb_cp_data, si->nr_wb_data,
> si->nr_flushing, si->nr_flushed,
> si->flush_list_empty);
> - seq_printf(s, "Discard: (%4d %4d)) cmd: %4d undiscard:%4u\n",
> - si->nr_discarding, si->nr_discarded,
> - si->nr_discard_cmd, si->undiscard_blks);
> + seq_printf(s, "Discard: (%4d %4d, avg:%4lldns, peak:%4lldns)) cmd: %4d undiscard:%4u\n",
> + si->nr_discarding, si->nr_discarded, ktime_to_us(si->discard_avg),
> + ktime_to_us(si->discard_peak), si->nr_discard_cmd, si->undiscard_blks);
> seq_printf(s, " - atomic IO: %4d (Max. %4d)\n",
> si->aw_cnt, si->max_aw_cnt);
> seq_printf(s, " - compress: %4d, hit:%8d\n", si->compress_pages, si->compress_page_hit);
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index e8953c3dc81a..2cd55cb981ff 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -371,6 +371,8 @@ struct discard_cmd {
> int error; /* bio error */
> spinlock_t lock; /* for state/bio_ref updating */
> unsigned short bio_ref; /* bio reference count */
> + struct discard_cmd_control *dcc; /* global discard cmd control */
> + ktime_t submit_start; /* submit start time */
> };
>
> enum {
> @@ -415,6 +417,9 @@ struct discard_cmd_control {
> unsigned int max_ordered_discard; /* maximum discard granularity issued by lba order */
> unsigned int undiscard_blks; /* # of undiscard blocks */
> unsigned int next_pos; /* next discard position */
> + spinlock_t discard_time_lock; /* for discard time statistics */
> + ktime_t discard_time_avg; /* issued discard cmd avg time */
> + ktime_t discard_time_peak; /* issued discard cmd peak time */
> atomic_t issued_discard; /* # of issued discard */
> atomic_t queued_discard; /* # of queued discard */
> atomic_t discard_cmd_cnt; /* # of cached cmd count */
> @@ -3896,6 +3901,7 @@ struct f2fs_stat_info {
> int nr_dio_read, nr_dio_write;
> unsigned int io_skip_bggc, other_skip_bggc;
> int nr_flushing, nr_flushed, flush_list_empty;
> + ktime_t discard_avg, discard_peak;
> int nr_discarding, nr_discarded;
> int nr_discard_cmd;
> unsigned int undiscard_blks;
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index a9099a754dd2..73cd05bb3f4a 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -937,6 +937,7 @@ static struct discard_cmd *__create_discard_cmd(struct f2fs_sb_info *sbi,
> list_add_tail(&dc->list, pend_list);
> spin_lock_init(&dc->lock);
> dc->bio_ref = 0;
> + dc->dcc = dcc;
> atomic_inc(&dcc->discard_cmd_cnt);
> dcc->undiscard_blks += len;
>
> @@ -1006,9 +1007,13 @@ static void __remove_discard_cmd(struct f2fs_sb_info *sbi,
> static void f2fs_submit_discard_endio(struct bio *bio)
> {
> struct discard_cmd *dc = (struct discard_cmd *)bio->bi_private;
> + struct discard_cmd_control *dcc = dc->dcc;
> unsigned long flags;
> + ktime_t submit_time;
> + int nr_discarded;
>
> spin_lock_irqsave(&dc->lock, flags);
> + submit_time = ktime_sub(ktime_get(), dc->submit_start);
> if (!dc->error)
> dc->error = blk_status_to_errno(bio->bi_status);
> dc->bio_ref--;
> @@ -1018,6 +1023,16 @@ static void f2fs_submit_discard_endio(struct bio *bio)
> }
> spin_unlock_irqrestore(&dc->lock, flags);
> bio_put(bio);
> +
> + spin_lock_irqsave(&dcc->discard_time_lock, flags);
> + nr_discarded = atomic_read(&dcc->issued_discard);
> + dcc->discard_time_avg = div_u64(ktime_add(nr_discarded * dcc->discard_time_avg,
> + submit_time),
> + nr_discarded + 1);
> + if (dcc->discard_time_avg > dcc->discard_time_peak)
> + dcc->discard_time_peak = dcc->discard_time_avg;
> + atomic_inc(&dcc->issued_discard);
> + spin_unlock_irqrestore(&dcc->discard_time_lock, flags);
Why not calculating average time only in update_general_status()? and here,
we just need to account total_{discard_time, discard_count} w/o additional
spinlock.
Thanks,
> }
>
> static void __check_sit_bitmap(struct f2fs_sb_info *sbi,
> @@ -1166,6 +1181,7 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi,
> * right away
> */
> spin_lock_irqsave(&dc->lock, flags);
> + dc->submit_start = ktime_get();
> if (last)
> dc->state = D_SUBMIT;
> else
> @@ -1185,8 +1201,6 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi,
> bio->bi_opf |= flag;
> submit_bio(bio);
>
> - atomic_inc(&dcc->issued_discard);
> -
> f2fs_update_iostat(sbi, NULL, FS_DISCARD, len * F2FS_BLKSIZE);
>
> lstart += len;
> @@ -2079,9 +2093,12 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
> INIT_LIST_HEAD(&dcc->wait_list);
> INIT_LIST_HEAD(&dcc->fstrim_list);
> mutex_init(&dcc->cmd_lock);
> + spin_lock_init(&dcc->discard_time_lock);
> atomic_set(&dcc->issued_discard, 0);
> atomic_set(&dcc->queued_discard, 0);
> atomic_set(&dcc->discard_cmd_cnt, 0);
> + dcc->discard_time_avg = 0;
> + dcc->discard_time_peak = 0;
> dcc->nr_discards = 0;
> dcc->max_discards = MAIN_SEGS(sbi) << sbi->log_blocks_per_seg;
> dcc->max_discard_request = DEF_MAX_DISCARD_REQUEST;
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