Re: [PATCH V2] f2fs: fix to avoid use GC_AT when setting gc_mode as GC_URGENT_LOW or GC_URGENT_MID

From: Chao Yu
Date: Mon Oct 28 2024 - 05:34:05 EST


On 2024/10/23 11:08, Zhiguo Niu wrote:
If gc_mode is set to GC_URGENT_LOW or GC_URGENT_MID, cost benefit GC
approach should be used, but if ATGC is enabled at the same time,
Age-threshold approach will be selected, which can only do amount of
GC and it is much less than the numbers of CB approach.

The code looks fine to me, there is one more thing, can you please update
description of gc_urgent in sysfs-fs-f2fs? so it can describe explicitly
that configuring gc_urgent to low or mid will setup GC_CB GC policy which
will override GC_AT.

Thanks,


some traces:
f2fs_gc-254:48-396 [007] ..... 2311600.684028: f2fs_gc_begin: dev = (254,48), gc_type = Background GC, no_background_GC = 0, nr_free_secs = 0, nodes = 1053, dents = 2, imeta = 18, free_sec:44898, free_seg:44898, rsv_seg:239, prefree_seg:0
f2fs_gc-254:48-396 [007] ..... 2311600.684527: f2fs_get_victim: dev = (254,48), type = No TYPE, policy = (Background GC, LFS-mode, Age-threshold), victim = 10, cost = 4294364975, ofs_unit = 1, pre_victim_secno = -1, prefree = 0, free = 44898
f2fs_gc-254:48-396 [007] ..... 2311600.714835: f2fs_gc_end: dev = (254,48), ret = 0, seg_freed = 0, sec_freed = 0, nodes = 1562, dents = 2, imeta = 18, free_sec:44898, free_seg:44898, rsv_seg:239, prefree_seg:0
f2fs_gc-254:48-396 [007] ..... 2311600.714843: f2fs_background_gc: dev = (254,48), wait_ms = 50, prefree = 0, free = 44898
f2fs_gc-254:48-396 [007] ..... 2311600.771785: f2fs_gc_begin: dev = (254,48), gc_type = Background GC, no_background_GC = 0, nr_free_secs = 0, nodes = 1562, dents = 2, imeta = 18, free_sec:44898, free_seg:44898, rsv_seg:239, prefree_seg:
f2fs_gc-254:48-396 [007] ..... 2311600.772275: f2fs_gc_end: dev = (254,48), ret = -61, seg_freed = 0, sec_freed = 0, nodes = 1562, dents = 2, imeta = 18, free_sec:44898, free_seg:44898, rsv_seg:239, prefree_seg:0

Fixes: 0e5e81114de1 ("f2fs: add GC_URGENT_LOW mode in gc_urgent")
Fixes: d98af5f45520 ("f2fs: introduce gc_urgent_mid mode")
Signed-off-by: Zhiguo Niu <zhiguo.niu@xxxxxxxxxx>
---
v2: make GC_URGENT_LOW also use CB approach
---
fs/f2fs/gc.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index e40bdd1..3e1b6d2 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -257,6 +257,8 @@ static int select_gc_type(struct f2fs_sb_info *sbi, int gc_type)
switch (sbi->gc_mode) {
case GC_IDLE_CB:
+ case GC_URGENT_LOW:
+ case GC_URGENT_MID:
gc_mode = GC_CB;
break;
case GC_IDLE_GREEDY: