Hi Pengyang,
Nice catch!
I think fggc_threshold needs to be revised, and we need to consider about
general victim selection as well.
Could you take a look at this?
>From 23b265f5ca6405032d092e240c94a827f743e42b Mon Sep 17 00:00:00 2001
From: Hou Pengyang <houpengy...@huawei.com>
Date: Thu, 16 Feb 2017 12:34:31 +0000
Subject: [PATCH] f2fs: add ovp valid_blocks check for bg gc victim to fg_gc
For foreground gc, greedy algorithm should be adapted, which makes
this formula work well:
(2 * (100 / config.overprovision + 1) + 6)
But currently, we fg_gc have a prior to select bg_gc victim segments to gc
first,
these victims are selected by cost-benefit algorithm, we can't guarantee such
segments
have the small valid blocks, which may destroy the f2fs rule, on the worstest
case, would
consume all the free segments.
This patch fix this by add a filter in check_bg_victims, if segment's has # of
valid blocks
over overprovision ratio, skip such segments.
Cc: <sta...@vger.kernel.org>
Signed-off-by: Hou Pengyang <houpengy...@huawei.com>
Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org>
---
fs/f2fs/f2fs.h | 3 +++
fs/f2fs/gc.c | 22 ++++++++++++++++++++--
fs/f2fs/segment.h | 9 +++++++++
3 files changed, 32 insertions(+), 2 deletions(-)
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index cc22dc458896..1c9f0cc8f027 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -888,6 +888,9 @@ struct f2fs_sb_info {
struct f2fs_gc_kthread *gc_thread; /* GC thread */
unsigned int cur_victim_sec; /* current victim section num */
+ /* threshold for converting bg victims for fg */
+ u64 fggc_threshold;
+
/* maximum # of trials to find a victim segment for SSR and GC */
unsigned int max_victim_search;
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 88e5e7b10ab6..fd4e479820e6 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -166,7 +166,8 @@ static void select_policy(struct f2fs_sb_info *sbi, int
gc_type,
p->ofs_unit = sbi->segs_per_sec;
}
- if (p->max_search > sbi->max_victim_search)
+ /* we need to check every dirty segments in the FG_GC case */
+ if (gc_type != FG_GC && p->max_search > sbi->max_victim_search)
p->max_search = sbi->max_victim_search;
p->offset = sbi->last_victim[p->gc_mode];
@@ -199,6 +200,10 @@ static unsigned int check_bg_victims(struct f2fs_sb_info
*sbi)
for_each_set_bit(secno, dirty_i->victim_secmap, MAIN_SECS(sbi)) {
if (sec_usage_check(sbi, secno))
continue;
+
+ if (no_fggc_candidate(sbi, secno))
+ continue;
+
clear_bit(secno, dirty_i->victim_secmap);
return secno * sbi->segs_per_sec;
}
@@ -322,13 +327,15 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
nsearched++;
}
-
secno = GET_SECNO(sbi, segno);
if (sec_usage_check(sbi, secno))
goto next;
if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap))
goto next;
+ if (gc_type == FG_GC && p.alloc_mode == LFS &&
+ no_fggc_candidate(sbi, secno))
+ goto next;
cost = get_gc_cost(sbi, segno, &p);
@@ -989,5 +996,16 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync, bool
background)
void build_gc_manager(struct f2fs_sb_info *sbi)
{
+ u64 user_block_count, ovp_count, blocks_per_sec, th;
+
DIRTY_I(sbi)->v_ops = &default_v_ops;
+
+ /* threshold of # of valid blocks in a section for victims of FG_GC */
+ user_block_count = sbi->user_block_count;
+ ovp_count = SM_I(sbi)->ovp_segments << sbi->log_blocks_per_seg;
+ blocks_per_sec = sbi->blocks_per_seg * sbi->segs_per_sec;
+
+ th = user_block_count * 100 * blocks_per_sec /
+ ((user_block_count + ovp_count) * 100);
+ sbi->fggc_threshold = th;
}
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index 5cb5755c75d9..f4020f141d83 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -716,6 +716,15 @@ static inline block_t sum_blk_addr(struct f2fs_sb_info
*sbi, int base, int type)
- (base + 1) + type;
}
+static inline bool no_fggc_candidate(struct f2fs_sb_info *sbi,
+ unsigned int secno)
+{
+ if (get_valid_blocks(sbi, secno, sbi->segs_per_sec) >=
+ sbi->fggc_threshold)
+ return true;
+ return false;
+}
+
static inline bool sec_usage_check(struct f2fs_sb_info *sbi, unsigned int
secno)
{
if (IS_CURSEC(sbi, secno) || (sbi->cur_victim_sec == secno))
--
2.11.0
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