linux-kernel - Re: [PATCH 1/2] f2fs: Optimize excessive write operations caused by continuous background garbage collection in Zoned UFS

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Message-ID: <9c5db535-f10e-4743-a8c7-e74f2680f2d0@vivo.com>
Date: Wed, 17 Sep 2025 15:15:38 +0800
From: Liao Yuanhong <liaoyuanhong@...o.com>
To: Jaegeuk Kim <jaegeuk@...nel.org>
Cc: Chao Yu <chao@...nel.org>,
 "open list:F2FS FILE SYSTEM" <linux-f2fs-devel@...ts.sourceforge.net>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] f2fs: Optimize excessive write operations caused by
 continuous background garbage collection in Zoned UFS


On 9/16/2025 10:28 AM, Jaegeuk Kim wrote:
> Could you please share some trends of relation between has_enough_free_blocks()
> vs. has_enough_dirty_blocks()? I'm wondering whethere there's a missing case
> where has_enough_free_blocks() is not enough.

Sure. I will find some time to test the data and create a table to see 
if there are any omissions.


Thanks,

Liao

> On 09/09, Liao Yuanhong wrote:
>> Incorporate a check using has_enough_dirty_blocks() to prevent redundant
>> background GC in Zoned UFS. When there are insufficient dirty segments,
>> continuous execution of background GC should be avoided, as it results in
>> unnecessary write operations and impacts device lifespan. The initial
>> threshold is set to 3 * section size (since f2fs data uses three write
>> pointers).
>>
>> Signed-off-by: Liao Yuanhong <liaoyuanhong@...o.com>
>> ---
>>   fs/f2fs/gc.c |  8 ++++++--
>>   fs/f2fs/gc.h | 10 +++++++++-
>>   2 files changed, 15 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>> index ed3acbfc83ca..4a8c08f970e3 100644
>> --- a/fs/f2fs/gc.c
>> +++ b/fs/f2fs/gc.c
>> @@ -120,7 +120,9 @@ static int gc_thread_func(void *data)
>>   
>>   		if (f2fs_sb_has_blkzoned(sbi)) {
>>   			if (has_enough_free_blocks(sbi,
>> -				gc_th->no_zoned_gc_percent)) {
>> +				gc_th->no_zoned_gc_percent) ||
>> +				!has_enough_dirty_blocks(sbi,
>> +				LIMIT_GC_DIRTY_SECTION_NUM)) {
>>   				wait_ms = gc_th->no_gc_sleep_time;
>>   				f2fs_up_write(&sbi->gc_lock);
>>   				goto next;
>> @@ -1750,7 +1752,9 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>   
>>   			if (f2fs_sb_has_blkzoned(sbi) &&
>>   					!has_enough_free_blocks(sbi,
>> -					sbi->gc_thread->boost_zoned_gc_percent))
>> +					sbi->gc_thread->boost_zoned_gc_percent) &&
>> +					has_enough_dirty_blocks(sbi,
>> +					LIMIT_GC_DIRTY_SECTION_NUM))
>>   				window_granularity *=
>>   					sbi->gc_thread->boost_gc_multiple;
>>   
>> diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
>> index 24e8b1c27acc..1ef234c2702b 100644
>> --- a/fs/f2fs/gc.h
>> +++ b/fs/f2fs/gc.h
>> @@ -36,6 +36,7 @@
>>   #define DEF_MIGRATION_WINDOW_GRANULARITY_ZONED	3
>>   #define BOOST_GC_MULTIPLE	5
>>   #define ZONED_PIN_SEC_REQUIRED_COUNT	1
>> +#define LIMIT_GC_DIRTY_SECTION_NUM	3
>>   
>>   #define DEF_GC_FAILED_PINNED_FILES	2048
>>   #define MAX_GC_FAILED_PINNED_FILES	USHRT_MAX
>> @@ -177,6 +178,12 @@ static inline bool has_enough_free_blocks(struct f2fs_sb_info *sbi,
>>   	return free_sections(sbi) > ((sbi->total_sections * limit_perc) / 100);
>>   }
>>   
>> +static inline bool has_enough_dirty_blocks(struct f2fs_sb_info *sbi,
>> +						unsigned int limit_num)
>> +{
>> +	return dirty_segments(sbi) > limit_num * SEGS_PER_SEC(sbi);
>> +}
>> +
>>   static inline bool has_enough_invalid_blocks(struct f2fs_sb_info *sbi)
>>   {
>>   	block_t user_block_count = sbi->user_block_count;
>> @@ -197,6 +204,7 @@ static inline bool need_to_boost_gc(struct f2fs_sb_info *sbi)
>>   {
>>   	if (f2fs_sb_has_blkzoned(sbi))
>>   		return !has_enough_free_blocks(sbi,
>> -				sbi->gc_thread->boost_zoned_gc_percent);
>> +				sbi->gc_thread->boost_zoned_gc_percent) &&
>> +				has_enough_dirty_blocks(sbi, LIMIT_GC_DIRTY_SECTION_NUM);
>>   	return has_enough_invalid_blocks(sbi);
>>   }
>> -- 
>> 2.34.1