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SubjectRe: [PATCH 2/5] f2fs: add cur_victim_sec for BG_GC to avoid skipping BG_GC victim
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On 2018/7/23 22:10, Yunlong Song wrote:
> If f2fs aborts BG_GC, then the section bit of victim_secmap will be set,
> which will cause the section skipped in the future get_victim of BG_GC.
> In a worst case that each section in the victim_secmap is set and there
> are enough free sections (so FG_GC can not be triggered), then BG_GC
> will skip all the sections and cannot find any victims, causing BG_GC

If f2fs aborts BG_GC, we'd better to clear victim_secmap?

> failed each time. Besides, SSR also uses BG_GC to get ssr segment, if

Looks like foreground GC will try to grab section which is selected as
victim of background GC?

Thanks,

> many sections in the victim_secmap are set, then SSR cannot get a proper
> ssr segment to allocate blocks, which makes SSR inefficiently. To fix
> this problem, we can add cur_victim_sec for BG_GC similar like that in
> FG_GC to avoid selecting the same section repeatedly.
>
> Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
> ---
> fs/f2fs/f2fs.h | 3 ++-
> fs/f2fs/gc.c | 15 +++++++++------
> fs/f2fs/segment.h | 3 ++-
> fs/f2fs/super.c | 3 ++-
> include/trace/events/f2fs.h | 18 ++++++++++++------
> 5 files changed, 27 insertions(+), 15 deletions(-)
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 57a8851..f8a7b42 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1217,7 +1217,8 @@ struct f2fs_sb_info {
> /* for cleaning operations */
> struct mutex gc_mutex; /* mutex for GC */
> struct f2fs_gc_kthread *gc_thread; /* GC thread */
> - unsigned int cur_victim_sec; /* current victim section num */
> + unsigned int cur_fg_victim_sec; /* current FG_GC victim section num */
> + unsigned int cur_bg_victim_sec; /* current BG_GC victim section num */
> unsigned int gc_mode; /* current GC state */
> /* for skip statistic */
> unsigned long long skipped_atomic_files[2]; /* FG_GC and BG_GC */
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 2ba470d..705d419 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -367,8 +367,6 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
>
> if (sec_usage_check(sbi, secno))
> goto next;
> - if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap))
> - goto next;
>
> cost = get_gc_cost(sbi, segno, &p);
>
> @@ -391,14 +389,17 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
> if (p.alloc_mode == LFS) {
> secno = GET_SEC_FROM_SEG(sbi, p.min_segno);
> if (gc_type == FG_GC)
> - sbi->cur_victim_sec = secno;
> - else
> + sbi->cur_fg_victim_sec = secno;
> + else {
> set_bit(secno, dirty_i->victim_secmap);
> + sbi->cur_bg_victim_sec = secno;
> + }
> }
> *result = (p.min_segno / p.ofs_unit) * p.ofs_unit;
>
> trace_f2fs_get_victim(sbi->sb, type, gc_type, &p,
> - sbi->cur_victim_sec,
> + sbi->cur_fg_victim_sec,
> + sbi->cur_bg_victim_sec,
> prefree_segments(sbi), free_segments(sbi));
> }
> out:
> @@ -1098,7 +1099,9 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> }
>
> if (gc_type == FG_GC)
> - sbi->cur_victim_sec = NULL_SEGNO;
> + sbi->cur_fg_victim_sec = NULL_SEGNO;
> + else
> + sbi->cur_bg_victim_sec = NULL_SEGNO;
>
> if (!sync) {
> if (has_not_enough_free_secs(sbi, sec_freed, 0)) {
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 5049551..b21bb96 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -787,7 +787,8 @@ static inline block_t sum_blk_addr(struct f2fs_sb_info *sbi, int base, int type)
>
> static inline bool sec_usage_check(struct f2fs_sb_info *sbi, unsigned int secno)
> {
> - if (IS_CURSEC(sbi, secno) || (sbi->cur_victim_sec == secno))
> + if (IS_CURSEC(sbi, secno) || (sbi->cur_fg_victim_sec == secno) ||
> + (sbi->cur_bg_victim_sec == secno))
> return true;
> return false;
> }
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 7187885..ef69ebf 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -2386,7 +2386,8 @@ static void init_sb_info(struct f2fs_sb_info *sbi)
> sbi->root_ino_num = le32_to_cpu(raw_super->root_ino);
> sbi->node_ino_num = le32_to_cpu(raw_super->node_ino);
> sbi->meta_ino_num = le32_to_cpu(raw_super->meta_ino);
> - sbi->cur_victim_sec = NULL_SECNO;
> + sbi->cur_fg_victim_sec = NULL_SECNO;
> + sbi->cur_bg_victim_sec = NULL_SECNO;
> sbi->max_victim_search = DEF_MAX_VICTIM_SEARCH;
>
> sbi->dir_level = DEF_DIR_LEVEL;
> diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
> index 7956989..0f01f82 100644
> --- a/include/trace/events/f2fs.h
> +++ b/include/trace/events/f2fs.h
> @@ -693,10 +693,12 @@
> TRACE_EVENT(f2fs_get_victim,
>
> TP_PROTO(struct super_block *sb, int type, int gc_type,
> - struct victim_sel_policy *p, unsigned int pre_victim,
> + struct victim_sel_policy *p, unsigned int pre_fg_victim,
> + unsigned int pre_bg_victim,
> unsigned int prefree, unsigned int free),
>
> - TP_ARGS(sb, type, gc_type, p, pre_victim, prefree, free),
> + TP_ARGS(sb, type, gc_type, p, pre_fg_victim, pre_bg_victim,
> + prefree, free),
>
> TP_STRUCT__entry(
> __field(dev_t, dev)
> @@ -707,7 +709,8 @@
> __field(unsigned int, victim)
> __field(unsigned int, cost)
> __field(unsigned int, ofs_unit)
> - __field(unsigned int, pre_victim)
> + __field(unsigned int, pre_fg_victim)
> + __field(unsigned int, pre_bg_victim)
> __field(unsigned int, prefree)
> __field(unsigned int, free)
> ),
> @@ -721,14 +724,16 @@
> __entry->victim = p->min_segno;
> __entry->cost = p->min_cost;
> __entry->ofs_unit = p->ofs_unit;
> - __entry->pre_victim = pre_victim;
> + __entry->pre_fg_victim = pre_fg_victim;
> + __entry->pre_bg_victim = pre_bg_victim;
> __entry->prefree = prefree;
> __entry->free = free;
> ),
>
> TP_printk("dev = (%d,%d), type = %s, policy = (%s, %s, %s), "
> "victim = %u, cost = %u, ofs_unit = %u, "
> - "pre_victim_secno = %d, prefree = %u, free = %u",
> + "pre_fg_victim_secno = %d, pre_bg_victim_secno = %d, "
> + "prefree = %u, free = %u",
> show_dev(__entry->dev),
> show_data_type(__entry->type),
> show_gc_type(__entry->gc_type),
> @@ -737,7 +742,8 @@
> __entry->victim,
> __entry->cost,
> __entry->ofs_unit,
> - (int)__entry->pre_victim,
> + (int)__entry->pre_fg_victim,
> + (int)__entry->pre_bg_victim,
> __entry->prefree,
> __entry->free)
> );
>

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