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Date: Wed, 22 Feb 2017 17:40:29 +0800
From: Chao Yu <yuchao0@...wei.com>
To: Jaegeuk Kim <jaegeuk@...nel.org>, <linux-kernel@...r.kernel.org>,
<linux-fsdevel@...r.kernel.org>,
<linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [PATCH 3/6] f2fs: remove batched discard in f2fs_trim_fs
On 2017/1/13 6:44, Jaegeuk Kim wrote:
> We don't need to do multiple checkpoints, since we don't actually wait for
> completion of discard commands during checkpoint.
> Instead, we still need to avoid very big discard commands, since that large
> discard can interfere block allocation.
I hope we can keep this functionality and related sysfs interface, the main
concern is that: for 16T size fragmented partition, at most there will be
~sizeof(u32)/2 4K blocks which could be invalid and needed to be discarded.
After removal of in-batch discard, we have to handle billions of discard message
with gc_mutex & cp_rwsem held, which will freeze f2fs for very long time.
So I suggest we just set trim_sections to 512 segments (covers one GB) by
default. How do you think?
Thanks,
>
> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> ---
> Documentation/ABI/testing/sysfs-fs-f2fs | 6 ------
> fs/f2fs/f2fs.h | 9 +-------
> fs/f2fs/segment.c | 38 +++++++++++----------------------
> fs/f2fs/super.c | 2 --
> 4 files changed, 14 insertions(+), 41 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> index a809f6005f14..df6b3f6e164a 100644
> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> @@ -75,12 +75,6 @@ Contact: "Jaegeuk Kim" <jaegeuk.kim@...sung.com>
> Description:
> Controls the memory footprint used by f2fs.
>
> -What: /sys/fs/f2fs/<disk>/trim_sections
> -Date: February 2015
> -Contact: "Jaegeuk Kim" <jaegeuk@...nel.org>
> -Description:
> - Controls the trimming rate in batch mode.
> -
> What: /sys/fs/f2fs/<disk>/cp_interval
> Date: October 2015
> Contact: "Jaegeuk Kim" <jaegeuk@...nel.org>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 548e75d18ec1..a2850bf2a487 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -128,11 +128,7 @@ enum {
> CP_DISCARD,
> };
>
> -#define DEF_BATCHED_TRIM_SECTIONS 2
> -#define BATCHED_TRIM_SEGMENTS(sbi) \
> - (SM_I(sbi)->trim_sections * (sbi)->segs_per_sec)
> -#define BATCHED_TRIM_BLOCKS(sbi) \
> - (BATCHED_TRIM_SEGMENTS(sbi) << (sbi)->log_blocks_per_seg)
> +#define MAX_DISCARD_BLOCKS(sbi) (1 << (sbi)->log_blocks_per_seg)
> #define DEF_CP_INTERVAL 60 /* 60 secs */
> #define DEF_IDLE_INTERVAL 5 /* 5 secs */
>
> @@ -638,9 +634,6 @@ struct f2fs_sm_info {
> int nr_discards; /* # of discards in the list */
> int max_discards; /* max. discards to be issued */
>
> - /* for batched trimming */
> - unsigned int trim_sections; /* # of sections to trim */
> -
> struct list_head sit_entry_set; /* sit entry set list */
>
> unsigned int ipu_policy; /* in-place-update policy */
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 73282108fa33..e6f3c6db7616 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -823,7 +823,8 @@ static void __add_discard_entry(struct f2fs_sb_info *sbi,
> if (!list_empty(head)) {
> last = list_last_entry(head, struct discard_entry, list);
> if (START_BLOCK(sbi, cpc->trim_start) + start ==
> - last->blkaddr + last->len) {
> + last->blkaddr + last->len &&
> + last->len <= MAX_DISCARD_BLOCKS(sbi)) {
> last->len += end - start;
> goto done;
> }
> @@ -1513,36 +1514,25 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
> "Found FS corruption, run fsck to fix.");
> goto out;
> }
> + if (sbi->discard_blks == 0)
> + goto out;
>
> /* start/end segment number in main_area */
> start_segno = (start <= MAIN_BLKADDR(sbi)) ? 0 : GET_SEGNO(sbi, start);
> end_segno = (end >= MAX_BLKADDR(sbi)) ? MAIN_SEGS(sbi) - 1 :
> GET_SEGNO(sbi, end);
> + /*
> + * do checkpoint to issue discard commands safely since we now can
> + * use async discard.
> + */
> cpc.reason = CP_DISCARD;
> cpc.trim_minlen = max_t(__u64, 1, F2FS_BYTES_TO_BLK(range->minlen));
> + cpc.trim_start = start_segno;
> + cpc.trim_end = end_segno;
>
> - /* do checkpoint to issue discard commands safely */
> - for (; start_segno <= end_segno; start_segno = cpc.trim_end + 1) {
> - cpc.trim_start = start_segno;
> -
> - if (sbi->discard_blks == 0)
> - break;
> - else if (sbi->discard_blks < BATCHED_TRIM_BLOCKS(sbi))
> - cpc.trim_end = end_segno;
> - else
> - cpc.trim_end = min_t(unsigned int,
> - rounddown(start_segno +
> - BATCHED_TRIM_SEGMENTS(sbi),
> - sbi->segs_per_sec) - 1, end_segno);
> -
> - mutex_lock(&sbi->gc_mutex);
> - err = write_checkpoint(sbi, &cpc);
> - mutex_unlock(&sbi->gc_mutex);
> - if (err)
> - break;
> -
> - schedule();
> - }
> + mutex_lock(&sbi->gc_mutex);
> + err = write_checkpoint(sbi, &cpc);
> + mutex_unlock(&sbi->gc_mutex);
> out:
> range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
> return err;
> @@ -2708,8 +2698,6 @@ int build_segment_manager(struct f2fs_sb_info *sbi)
> sm_info->nr_discards = 0;
> sm_info->max_discards = 0;
>
> - sm_info->trim_sections = DEF_BATCHED_TRIM_SECTIONS;
> -
> INIT_LIST_HEAD(&sm_info->sit_entry_set);
>
> if (test_opt(sbi, FLUSH_MERGE) && !f2fs_readonly(sbi->sb)) {
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 461c29043aec..37d40d8aa9c4 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -284,7 +284,6 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_no_gc_sleep_time, no_gc_sleep_time);
> F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
> F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
> F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, max_small_discards, max_discards);
> -F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
> F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
> F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_ipu_util, min_ipu_util);
> F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_fsync_blocks, min_fsync_blocks);
> @@ -309,7 +308,6 @@ static struct attribute *f2fs_attrs[] = {
> ATTR_LIST(gc_idle),
> ATTR_LIST(reclaim_segments),
> ATTR_LIST(max_small_discards),
> - ATTR_LIST(batched_trim_sections),
> ATTR_LIST(ipu_policy),
> ATTR_LIST(min_ipu_util),
> ATTR_LIST(min_fsync_blocks),
>
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