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* [f2fs-dev] [PATCH 1/3] f2fs: skip GC when section is full
@ 2020-02-14 18:58 Jaegeuk Kim
  2020-02-14 18:58 ` [f2fs-dev] [PATCH 2/3] f2fs: add migration count iff migration happens Jaegeuk Kim
                   ` (2 more replies)
  0 siblings, 3 replies; 13+ messages in thread
From: Jaegeuk Kim @ 2020-02-14 18:58 UTC (permalink / raw)
  To: linux-kernel, linux-f2fs-devel; +Cc: Jaegeuk Kim

This fixes skipping GC when segment is full in large section.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 fs/f2fs/gc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 53312d7bc78b..65c0687ee2bb 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1018,8 +1018,8 @@ static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 		 * race condition along with SSR block allocation.
 		 */
 		if ((gc_type == BG_GC && has_not_enough_free_secs(sbi, 0, 0)) ||
-				get_valid_blocks(sbi, segno, false) ==
-							sbi->blocks_per_seg)
+				get_valid_blocks(sbi, segno, true) ==
+							BLKS_PER_SEC(sbi))
 			return submitted;
 
 		if (check_valid_map(sbi, segno, off) == 0)
-- 
2.25.0.265.gbab2e86ba0-goog



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^ permalink raw reply related	[flat|nested] 13+ messages in thread

* [f2fs-dev] [PATCH 2/3] f2fs: add migration count iff migration happens
  2020-02-14 18:58 [f2fs-dev] [PATCH 1/3] f2fs: skip GC when section is full Jaegeuk Kim
@ 2020-02-14 18:58 ` Jaegeuk Kim
  2020-02-17  1:41   ` Chao Yu
  2020-02-17  1:43   ` Chao Yu
  2020-02-14 18:58 ` [f2fs-dev] [PATCH 3/3] f2fs: skip migration only when BG_GC is called Jaegeuk Kim
  2020-02-17  1:40 ` [f2fs-dev] [PATCH 1/3] f2fs: skip GC when section is full Chao Yu
  2 siblings, 2 replies; 13+ messages in thread
From: Jaegeuk Kim @ 2020-02-14 18:58 UTC (permalink / raw)
  To: linux-kernel, linux-f2fs-devel; +Cc: Jaegeuk Kim

If first segment is empty and migration_granularity is 1, we can't move this
at all.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 fs/f2fs/gc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 65c0687ee2bb..bbf4db3f6bb4 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1233,12 +1233,12 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
 							segno, gc_type);
 
 		stat_inc_seg_count(sbi, type, gc_type);
+		migrated++;
 
 freed:
 		if (gc_type == FG_GC &&
 				get_valid_blocks(sbi, segno, false) == 0)
 			seg_freed++;
-		migrated++;
 
 		if (__is_large_section(sbi) && segno + 1 < end_segno)
 			sbi->next_victim_seg[gc_type] = segno + 1;
-- 
2.25.0.265.gbab2e86ba0-goog



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^ permalink raw reply related	[flat|nested] 13+ messages in thread

* [f2fs-dev] [PATCH 3/3] f2fs: skip migration only when BG_GC is called
  2020-02-14 18:58 [f2fs-dev] [PATCH 1/3] f2fs: skip GC when section is full Jaegeuk Kim
  2020-02-14 18:58 ` [f2fs-dev] [PATCH 2/3] f2fs: add migration count iff migration happens Jaegeuk Kim
@ 2020-02-14 18:58 ` Jaegeuk Kim
  2020-02-17  2:22   ` Chao Yu
  2020-02-17  1:40 ` [f2fs-dev] [PATCH 1/3] f2fs: skip GC when section is full Chao Yu
  2 siblings, 1 reply; 13+ messages in thread
From: Jaegeuk Kim @ 2020-02-14 18:58 UTC (permalink / raw)
  To: linux-kernel, linux-f2fs-devel; +Cc: Jaegeuk Kim

FG_GC needs to move entire section more quickly.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 fs/f2fs/gc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index bbf4db3f6bb4..1676eebc8c8b 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1203,7 +1203,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
 
 		if (get_valid_blocks(sbi, segno, false) == 0)
 			goto freed;
-		if (__is_large_section(sbi) &&
+		if (gc_type == BG_GC && __is_large_section(sbi) &&
 				migrated >= sbi->migration_granularity)
 			goto skip;
 		if (!PageUptodate(sum_page) || unlikely(f2fs_cp_error(sbi)))
-- 
2.25.0.265.gbab2e86ba0-goog



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^ permalink raw reply related	[flat|nested] 13+ messages in thread

* Re: [f2fs-dev] [PATCH 1/3] f2fs: skip GC when section is full
  2020-02-14 18:58 [f2fs-dev] [PATCH 1/3] f2fs: skip GC when section is full Jaegeuk Kim
  2020-02-14 18:58 ` [f2fs-dev] [PATCH 2/3] f2fs: add migration count iff migration happens Jaegeuk Kim
  2020-02-14 18:58 ` [f2fs-dev] [PATCH 3/3] f2fs: skip migration only when BG_GC is called Jaegeuk Kim
@ 2020-02-17  1:40 ` Chao Yu
  2 siblings, 0 replies; 13+ messages in thread
From: Chao Yu @ 2020-02-17  1:40 UTC (permalink / raw)
  To: Jaegeuk Kim, linux-kernel, linux-f2fs-devel

On 2020/2/15 2:58, Jaegeuk Kim wrote:
> This fixes skipping GC when segment is full in large section.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/gc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 53312d7bc78b..65c0687ee2bb 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -1018,8 +1018,8 @@ static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>  		 * race condition along with SSR block allocation.
>  		 */
>  		if ((gc_type == BG_GC && has_not_enough_free_secs(sbi, 0, 0)) ||
> -				get_valid_blocks(sbi, segno, false) ==
> -							sbi->blocks_per_seg)
> +				get_valid_blocks(sbi, segno, true) ==
> +							BLKS_PER_SEC(sbi))

Then in large section, if current segment is all valid, we won't skip scanning
it, so do we need to change like this:

if ((gc_type == BG_GC && has_not_enough_free_secs(sbi, 0, 0)) ||
	get_valid_blocks(sbi, segno, false) == sbi->blocks_per_seg ||
	get_valid_blocks(sbi, segno, true) == BLKS_PER_SEC(sbi))
	return submitted;

>  			return submitted;
>  
>  		if (check_valid_map(sbi, segno, off) == 0)
> 


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^ permalink raw reply	[flat|nested] 13+ messages in thread

* Re: [f2fs-dev] [PATCH 2/3] f2fs: add migration count iff migration happens
  2020-02-14 18:58 ` [f2fs-dev] [PATCH 2/3] f2fs: add migration count iff migration happens Jaegeuk Kim
@ 2020-02-17  1:41   ` Chao Yu
  2020-02-17  1:43   ` Chao Yu
  1 sibling, 0 replies; 13+ messages in thread
From: Chao Yu @ 2020-02-17  1:41 UTC (permalink / raw)
  To: Jaegeuk Kim, linux-kernel, linux-f2fs-devel

On 2020/2/15 2:58, Jaegeuk Kim wrote:
> If first segment is empty and migration_granularity is 1, we can't move this
> at all.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,


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^ permalink raw reply	[flat|nested] 13+ messages in thread

* Re: [f2fs-dev] [PATCH 2/3] f2fs: add migration count iff migration happens
  2020-02-14 18:58 ` [f2fs-dev] [PATCH 2/3] f2fs: add migration count iff migration happens Jaegeuk Kim
  2020-02-17  1:41   ` Chao Yu
@ 2020-02-17  1:43   ` Chao Yu
  1 sibling, 0 replies; 13+ messages in thread
From: Chao Yu @ 2020-02-17  1:43 UTC (permalink / raw)
  To: Jaegeuk Kim, linux-kernel, linux-f2fs-devel

BTW

f2fs: add migration count iff migration happens

typo: iff

On 2020/2/15 2:58, Jaegeuk Kim wrote:
> If first segment is empty and migration_granularity is 1, we can't move this
> at all.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/gc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 65c0687ee2bb..bbf4db3f6bb4 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -1233,12 +1233,12 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>  							segno, gc_type);
>  
>  		stat_inc_seg_count(sbi, type, gc_type);
> +		migrated++;
>  
>  freed:
>  		if (gc_type == FG_GC &&
>  				get_valid_blocks(sbi, segno, false) == 0)
>  			seg_freed++;
> -		migrated++;
>  
>  		if (__is_large_section(sbi) && segno + 1 < end_segno)
>  			sbi->next_victim_seg[gc_type] = segno + 1;
> 


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^ permalink raw reply	[flat|nested] 13+ messages in thread

* Re: [f2fs-dev] [PATCH 3/3] f2fs: skip migration only when BG_GC is called
  2020-02-14 18:58 ` [f2fs-dev] [PATCH 3/3] f2fs: skip migration only when BG_GC is called Jaegeuk Kim
@ 2020-02-17  2:22   ` Chao Yu
  2020-02-18 23:27     ` Jaegeuk Kim
  0 siblings, 1 reply; 13+ messages in thread
From: Chao Yu @ 2020-02-17  2:22 UTC (permalink / raw)
  To: Jaegeuk Kim, linux-kernel, linux-f2fs-devel

On 2020/2/15 2:58, Jaegeuk Kim wrote:
> FG_GC needs to move entire section more quickly.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/gc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index bbf4db3f6bb4..1676eebc8c8b 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -1203,7 +1203,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>  
>  		if (get_valid_blocks(sbi, segno, false) == 0)
>  			goto freed;
> -		if (__is_large_section(sbi) &&
> +		if (gc_type == BG_GC && __is_large_section(sbi) &&
>  				migrated >= sbi->migration_granularity)

I knew migrating one large section is a more efficient way, but this can
increase long-tail latency of f2fs_balance_fs() occasionally, especially in
extreme fragmented space.

Thanks,

>  			goto skip;
>  		if (!PageUptodate(sum_page) || unlikely(f2fs_cp_error(sbi)))
> 


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^ permalink raw reply	[flat|nested] 13+ messages in thread

* Re: [f2fs-dev] [PATCH 3/3] f2fs: skip migration only when BG_GC is called
  2020-02-17  2:22   ` Chao Yu
@ 2020-02-18 23:27     ` Jaegeuk Kim
  2020-02-19  3:01       ` Chao Yu
  0 siblings, 1 reply; 13+ messages in thread
From: Jaegeuk Kim @ 2020-02-18 23:27 UTC (permalink / raw)
  To: Chao Yu; +Cc: linux-kernel, linux-f2fs-devel

On 02/17, Chao Yu wrote:
> On 2020/2/15 2:58, Jaegeuk Kim wrote:
> > FG_GC needs to move entire section more quickly.
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> >  fs/f2fs/gc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index bbf4db3f6bb4..1676eebc8c8b 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -1203,7 +1203,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
> >  
> >  		if (get_valid_blocks(sbi, segno, false) == 0)
> >  			goto freed;
> > -		if (__is_large_section(sbi) &&
> > +		if (gc_type == BG_GC && __is_large_section(sbi) &&
> >  				migrated >= sbi->migration_granularity)
> 
> I knew migrating one large section is a more efficient way, but this can
> increase long-tail latency of f2fs_balance_fs() occasionally, especially in
> extreme fragmented space.

FG_GC requires to wait for whole section migration which shows the entire
latency.

> 
> Thanks,
> 
> >  			goto skip;
> >  		if (!PageUptodate(sum_page) || unlikely(f2fs_cp_error(sbi)))
> > 


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^ permalink raw reply	[flat|nested] 13+ messages in thread

* Re: [f2fs-dev] [PATCH 3/3] f2fs: skip migration only when BG_GC is called
  2020-02-18 23:27     ` Jaegeuk Kim
@ 2020-02-19  3:01       ` Chao Yu
  2020-02-19  3:04         ` Jaegeuk Kim
  0 siblings, 1 reply; 13+ messages in thread
From: Chao Yu @ 2020-02-19  3:01 UTC (permalink / raw)
  To: Jaegeuk Kim; +Cc: linux-kernel, linux-f2fs-devel

On 2020/2/19 7:27, Jaegeuk Kim wrote:
> On 02/17, Chao Yu wrote:
>> On 2020/2/15 2:58, Jaegeuk Kim wrote:
>>> FG_GC needs to move entire section more quickly.
>>>
>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
>>> ---
>>>  fs/f2fs/gc.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>> index bbf4db3f6bb4..1676eebc8c8b 100644
>>> --- a/fs/f2fs/gc.c
>>> +++ b/fs/f2fs/gc.c
>>> @@ -1203,7 +1203,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>>  
>>>  		if (get_valid_blocks(sbi, segno, false) == 0)
>>>  			goto freed;
>>> -		if (__is_large_section(sbi) &&
>>> +		if (gc_type == BG_GC && __is_large_section(sbi) &&
>>>  				migrated >= sbi->migration_granularity)
>>
>> I knew migrating one large section is a more efficient way, but this can
>> increase long-tail latency of f2fs_balance_fs() occasionally, especially in
>> extreme fragmented space.
> 
> FG_GC requires to wait for whole section migration which shows the entire
> latency.

That will cause long-tail latency for single f2fs_balance_fs() procedure,
which it looks a very long hang when userspace call f2fs syscall, so why
not splitting total elapsed time into several f2fs_balance_fs() to avoid that.

Thanks,

> 
>>
>> Thanks,
>>
>>>  			goto skip;
>>>  		if (!PageUptodate(sum_page) || unlikely(f2fs_cp_error(sbi)))
>>>
> .
> 


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^ permalink raw reply	[flat|nested] 13+ messages in thread

* Re: [f2fs-dev] [PATCH 3/3] f2fs: skip migration only when BG_GC is called
  2020-02-19  3:01       ` Chao Yu
@ 2020-02-19  3:04         ` Jaegeuk Kim
  2020-02-19  3:54           ` Chao Yu
  0 siblings, 1 reply; 13+ messages in thread
From: Jaegeuk Kim @ 2020-02-19  3:04 UTC (permalink / raw)
  To: Chao Yu; +Cc: linux-kernel, linux-f2fs-devel

On 02/19, Chao Yu wrote:
> On 2020/2/19 7:27, Jaegeuk Kim wrote:
> > On 02/17, Chao Yu wrote:
> >> On 2020/2/15 2:58, Jaegeuk Kim wrote:
> >>> FG_GC needs to move entire section more quickly.
> >>>
> >>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> >>> ---
> >>>  fs/f2fs/gc.c | 2 +-
> >>>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> >>> index bbf4db3f6bb4..1676eebc8c8b 100644
> >>> --- a/fs/f2fs/gc.c
> >>> +++ b/fs/f2fs/gc.c
> >>> @@ -1203,7 +1203,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
> >>>  
> >>>  		if (get_valid_blocks(sbi, segno, false) == 0)
> >>>  			goto freed;
> >>> -		if (__is_large_section(sbi) &&
> >>> +		if (gc_type == BG_GC && __is_large_section(sbi) &&
> >>>  				migrated >= sbi->migration_granularity)
> >>
> >> I knew migrating one large section is a more efficient way, but this can
> >> increase long-tail latency of f2fs_balance_fs() occasionally, especially in
> >> extreme fragmented space.
> > 
> > FG_GC requires to wait for whole section migration which shows the entire
> > latency.
> 
> That will cause long-tail latency for single f2fs_balance_fs() procedure,
> which it looks a very long hang when userspace call f2fs syscall, so why
> not splitting total elapsed time into several f2fs_balance_fs() to avoid that.

Then, other ops can easily make more dirty segments. The intention of FG_GC is
to block everything and make min. free segments as a best shot.

> 
> Thanks,
> 
> > 
> >>
> >> Thanks,
> >>
> >>>  			goto skip;
> >>>  		if (!PageUptodate(sum_page) || unlikely(f2fs_cp_error(sbi)))
> >>>
> > .
> > 


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^ permalink raw reply	[flat|nested] 13+ messages in thread

* Re: [f2fs-dev] [PATCH 3/3] f2fs: skip migration only when BG_GC is called
  2020-02-19  3:04         ` Jaegeuk Kim
@ 2020-02-19  3:54           ` Chao Yu
  2020-02-24 21:53             ` Jaegeuk Kim
  0 siblings, 1 reply; 13+ messages in thread
From: Chao Yu @ 2020-02-19  3:54 UTC (permalink / raw)
  To: Jaegeuk Kim; +Cc: linux-kernel, linux-f2fs-devel

On 2020/2/19 11:04, Jaegeuk Kim wrote:
> On 02/19, Chao Yu wrote:
>> On 2020/2/19 7:27, Jaegeuk Kim wrote:
>>> On 02/17, Chao Yu wrote:
>>>> On 2020/2/15 2:58, Jaegeuk Kim wrote:
>>>>> FG_GC needs to move entire section more quickly.
>>>>>
>>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
>>>>> ---
>>>>>  fs/f2fs/gc.c | 2 +-
>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>>>> index bbf4db3f6bb4..1676eebc8c8b 100644
>>>>> --- a/fs/f2fs/gc.c
>>>>> +++ b/fs/f2fs/gc.c
>>>>> @@ -1203,7 +1203,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>>>>  
>>>>>  		if (get_valid_blocks(sbi, segno, false) == 0)
>>>>>  			goto freed;
>>>>> -		if (__is_large_section(sbi) &&
>>>>> +		if (gc_type == BG_GC && __is_large_section(sbi) &&
>>>>>  				migrated >= sbi->migration_granularity)
>>>>
>>>> I knew migrating one large section is a more efficient way, but this can
>>>> increase long-tail latency of f2fs_balance_fs() occasionally, especially in
>>>> extreme fragmented space.
>>>
>>> FG_GC requires to wait for whole section migration which shows the entire
>>> latency.
>>
>> That will cause long-tail latency for single f2fs_balance_fs() procedure,
>> which it looks a very long hang when userspace call f2fs syscall, so why
>> not splitting total elapsed time into several f2fs_balance_fs() to avoid that.
> 
> Then, other ops can easily make more dirty segments. The intention of FG_GC is

Yup, that's a problem, if there are more dirty datas being made, reserved segments
may be ran out during FG_GC.

> to block everything and make min. free segments as a best shot.

I just try to simulate write GC's logic in FTL to mitigate single op's max latency,
otherwise benchmark looks hang during FG_GC (in a 500mb+ section).

Thanks,

> 
>>
>> Thanks,
>>
>>>
>>>>
>>>> Thanks,
>>>>
>>>>>  			goto skip;
>>>>>  		if (!PageUptodate(sum_page) || unlikely(f2fs_cp_error(sbi)))
>>>>>
>>> .
>>>
> .
> 


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^ permalink raw reply	[flat|nested] 13+ messages in thread

* Re: [f2fs-dev] [PATCH 3/3] f2fs: skip migration only when BG_GC is called
  2020-02-19  3:54           ` Chao Yu
@ 2020-02-24 21:53             ` Jaegeuk Kim
  2020-02-25  2:24               ` Chao Yu
  0 siblings, 1 reply; 13+ messages in thread
From: Jaegeuk Kim @ 2020-02-24 21:53 UTC (permalink / raw)
  To: Chao Yu; +Cc: linux-kernel, linux-f2fs-devel

On 02/19, Chao Yu wrote:
> On 2020/2/19 11:04, Jaegeuk Kim wrote:
> > On 02/19, Chao Yu wrote:
> >> On 2020/2/19 7:27, Jaegeuk Kim wrote:
> >>> On 02/17, Chao Yu wrote:
> >>>> On 2020/2/15 2:58, Jaegeuk Kim wrote:
> >>>>> FG_GC needs to move entire section more quickly.
> >>>>>
> >>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> >>>>> ---
> >>>>>  fs/f2fs/gc.c | 2 +-
> >>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>>>>
> >>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> >>>>> index bbf4db3f6bb4..1676eebc8c8b 100644
> >>>>> --- a/fs/f2fs/gc.c
> >>>>> +++ b/fs/f2fs/gc.c
> >>>>> @@ -1203,7 +1203,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
> >>>>>  
> >>>>>  		if (get_valid_blocks(sbi, segno, false) == 0)
> >>>>>  			goto freed;
> >>>>> -		if (__is_large_section(sbi) &&
> >>>>> +		if (gc_type == BG_GC && __is_large_section(sbi) &&
> >>>>>  				migrated >= sbi->migration_granularity)
> >>>>
> >>>> I knew migrating one large section is a more efficient way, but this can
> >>>> increase long-tail latency of f2fs_balance_fs() occasionally, especially in
> >>>> extreme fragmented space.
> >>>
> >>> FG_GC requires to wait for whole section migration which shows the entire
> >>> latency.
> >>
> >> That will cause long-tail latency for single f2fs_balance_fs() procedure,
> >> which it looks a very long hang when userspace call f2fs syscall, so why
> >> not splitting total elapsed time into several f2fs_balance_fs() to avoid that.
> > 
> > Then, other ops can easily make more dirty segments. The intention of FG_GC is
> 
> Yup, that's a problem, if there are more dirty datas being made, reserved segments
> may be ran out during FG_GC.
> 
> > to block everything and make min. free segments as a best shot.
> 
> I just try to simulate write GC's logic in FTL to mitigate single op's max latency,
> otherwise benchmark looks hang during FG_GC (in a 500mb+ section).

Hmm, I think we may need to think another way like doing BG_GC more aggressively.

> 
> Thanks,
> 
> > 
> >>
> >> Thanks,
> >>
> >>>
> >>>>
> >>>> Thanks,
> >>>>
> >>>>>  			goto skip;
> >>>>>  		if (!PageUptodate(sum_page) || unlikely(f2fs_cp_error(sbi)))
> >>>>>
> >>> .
> >>>
> > .
> > 


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https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

^ permalink raw reply	[flat|nested] 13+ messages in thread

* Re: [f2fs-dev] [PATCH 3/3] f2fs: skip migration only when BG_GC is called
  2020-02-24 21:53             ` Jaegeuk Kim
@ 2020-02-25  2:24               ` Chao Yu
  0 siblings, 0 replies; 13+ messages in thread
From: Chao Yu @ 2020-02-25  2:24 UTC (permalink / raw)
  To: Jaegeuk Kim; +Cc: linux-kernel, linux-f2fs-devel

On 2020/2/25 5:53, Jaegeuk Kim wrote:
> On 02/19, Chao Yu wrote:
>> On 2020/2/19 11:04, Jaegeuk Kim wrote:
>>> On 02/19, Chao Yu wrote:
>>>> On 2020/2/19 7:27, Jaegeuk Kim wrote:
>>>>> On 02/17, Chao Yu wrote:
>>>>>> On 2020/2/15 2:58, Jaegeuk Kim wrote:
>>>>>>> FG_GC needs to move entire section more quickly.
>>>>>>>
>>>>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
>>>>>>> ---
>>>>>>>  fs/f2fs/gc.c | 2 +-
>>>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>>>>>> index bbf4db3f6bb4..1676eebc8c8b 100644
>>>>>>> --- a/fs/f2fs/gc.c
>>>>>>> +++ b/fs/f2fs/gc.c
>>>>>>> @@ -1203,7 +1203,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>>>>>>  
>>>>>>>  		if (get_valid_blocks(sbi, segno, false) == 0)
>>>>>>>  			goto freed;
>>>>>>> -		if (__is_large_section(sbi) &&
>>>>>>> +		if (gc_type == BG_GC && __is_large_section(sbi) &&
>>>>>>>  				migrated >= sbi->migration_granularity)
>>>>>>
>>>>>> I knew migrating one large section is a more efficient way, but this can
>>>>>> increase long-tail latency of f2fs_balance_fs() occasionally, especially in
>>>>>> extreme fragmented space.
>>>>>
>>>>> FG_GC requires to wait for whole section migration which shows the entire
>>>>> latency.
>>>>
>>>> That will cause long-tail latency for single f2fs_balance_fs() procedure,
>>>> which it looks a very long hang when userspace call f2fs syscall, so why
>>>> not splitting total elapsed time into several f2fs_balance_fs() to avoid that.
>>>
>>> Then, other ops can easily make more dirty segments. The intention of FG_GC is
>>
>> Yup, that's a problem, if there are more dirty datas being made, reserved segments
>> may be ran out during FG_GC.
>>
>>> to block everything and make min. free segments as a best shot.
>>
>> I just try to simulate write GC's logic in FTL to mitigate single op's max latency,
>> otherwise benchmark looks hang during FG_GC (in a 500mb+ section).

Oh, if we want to FG_GC only migrate on segment on time, it needs to change
has_not_enough_free_secs() condition as well, so previous logic is broken.

Nvm, please add:

Reviewed-by: Chao Yu <yuchao0@huawei.com>

> 
> Hmm, I think we may need to think another way like doing BG_GC more aggressively.

Agreed, I guess SMR scenario may need such policy: higher trigger frequency on bggc
when free space decreases, but less block migration for each bggc cycle.

Thanks,

> 
>>
>> Thanks,
>>
>>>
>>>>
>>>> Thanks,
>>>>
>>>>>
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>>>  			goto skip;
>>>>>>>  		if (!PageUptodate(sum_page) || unlikely(f2fs_cp_error(sbi)))
>>>>>>>
>>>>> .
>>>>>
>>> .
>>>
> .
> 


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^ permalink raw reply	[flat|nested] 13+ messages in thread

end of thread, other threads:[~2020-02-25  2:24 UTC | newest]

Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-02-14 18:58 [f2fs-dev] [PATCH 1/3] f2fs: skip GC when section is full Jaegeuk Kim
2020-02-14 18:58 ` [f2fs-dev] [PATCH 2/3] f2fs: add migration count iff migration happens Jaegeuk Kim
2020-02-17  1:41   ` Chao Yu
2020-02-17  1:43   ` Chao Yu
2020-02-14 18:58 ` [f2fs-dev] [PATCH 3/3] f2fs: skip migration only when BG_GC is called Jaegeuk Kim
2020-02-17  2:22   ` Chao Yu
2020-02-18 23:27     ` Jaegeuk Kim
2020-02-19  3:01       ` Chao Yu
2020-02-19  3:04         ` Jaegeuk Kim
2020-02-19  3:54           ` Chao Yu
2020-02-24 21:53             ` Jaegeuk Kim
2020-02-25  2:24               ` Chao Yu
2020-02-17  1:40 ` [f2fs-dev] [PATCH 1/3] f2fs: skip GC when section is full Chao Yu

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