On 2016/9/20 10:54, Jaegeuk Kim wrote:
> On Tue, Sep 20, 2016 at 10:22:22AM +0800, Chao Yu wrote:
>> Hi Jaegeuk,
>>
>> On 2016/9/20 6:12, Jaegeuk Kim wrote:
>>> Hi Chao,
>>>
>>> On Sun, Sep 18, 2016 at 07:52:27PM +0800, Chao Yu wrote:
>>>> Previously, we will choose to speed up background gc when the below
>>>> conditions are both satisfied:
>>>> a. There are a number of invalid blocks
>>>> b. There is not enough free space
>>>>
>>>> But, when space utilization is high (utilization > 60%), there will be
>>>> not enough invalid blocks, result in slowing down background gc, after
>>>> then there are more opportunities that triggering foreground gc due to
>>>> high fragmented free space in fs.
>>>>
>>>> Remove condition a) in order to avoid slow down background gc speed in
>>>> a high utilization fs.
>>>
>>> There exists a trade-off here: wear-out vs. eager gc for future speed-up.
>>> How about using a kind of f2fs's dirty level (e.g., BDF)?
>>
>> Yep, I think that f2fs can implement a mechanism which can provide more
>> dynamically adjustable GC speed in the specified scenario of user, by this,
>> user
>> can choose the strategy which is more beneficial to aspect
>> (wear-out/performance) they care. Let me think a while, anyway I agree that
>> BDF
>> is a good reference value here.
>>
>> And Before we can provide above ability, how about treat this patch as a
>> fixing
>> patch, since it fixes to not adjust speed of GC according to utilization
>> watermark?
>
> Well, this is not a bug fix, but a very conservative policy. So, please let's
> make a better policy, if possible.
Alright, let's think about this.
Thanks,
>
> Thanks,
>
>>
>> Thanks,
>>
>>>
>>> Thanks,
>>>
>>>>
>>>> Signed-off-by: Chao Yu <yuch...@huawei.com>
>>>> ---
>>>> fs/f2fs/gc.h | 18 +++---------------
>>>> 1 file changed, 3 insertions(+), 15 deletions(-)
>>>>
>>>> diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
>>>> index a993967..5d0a19c 100644
>>>> --- a/fs/f2fs/gc.h
>>>> +++ b/fs/f2fs/gc.h
>>>> @@ -16,7 +16,6 @@
>>>> #define DEF_GC_THREAD_MIN_SLEEP_TIME 30000 /* milliseconds */
>>>> #define DEF_GC_THREAD_MAX_SLEEP_TIME 60000
>>>> #define DEF_GC_THREAD_NOGC_SLEEP_TIME 300000 /* wait 5 min */
>>>> -#define LIMIT_INVALID_BLOCK 40 /* percentage over total user space
>>>> */
>>>> #define LIMIT_FREE_BLOCK 40 /* percentage over invalid + free space */
>>>>
>>>> /* Search max. number of dirty segments to select a victim segment */
>>>> @@ -52,11 +51,6 @@ static inline block_t free_user_blocks(struct
>>>> f2fs_sb_info *sbi)
>>>> << sbi->log_blocks_per_seg;
>>>> }
>>>>
>>>> -static inline block_t limit_invalid_user_blocks(struct f2fs_sb_info *sbi)
>>>> -{
>>>> - return (long)(sbi->user_block_count * LIMIT_INVALID_BLOCK) / 100;
>>>> -}
>>>> -
>>>> static inline block_t limit_free_user_blocks(struct f2fs_sb_info *sbi)
>>>> {
>>>> block_t reclaimable_user_blocks = sbi->user_block_count -
>>>> @@ -88,15 +82,9 @@ static inline void decrease_sleep_time(struct
>>>> f2fs_gc_kthread *gc_th,
>>>>
>>>> static inline bool has_enough_invalid_blocks(struct f2fs_sb_info *sbi)
>>>> {
>>>> - block_t invalid_user_blocks = sbi->user_block_count -
>>>> - written_block_count(sbi);
>>>> /*
>>>> - * Background GC is triggered with the following conditions.
>>>> - * 1. There are a number of invalid blocks.
>>>> - * 2. There is not enough free space.
>>>> + * Background GC should speed up when there is not enough free blocks
>>>> + * in total unused (free + invalid) blocks.
>>>> */
>>>> - if (invalid_user_blocks > limit_invalid_user_blocks(sbi) &&
>>>> - free_user_blocks(sbi) < limit_free_user_blocks(sbi))
>>>> - return true;
>>>> - return false;
>>>> + return free_user_blocks(sbi) < limit_free_user_blocks(sbi);
>>>> }
>>>> --
>>>> 2.8.2.311.gee88674
>>>
>>> .
>>>
>
> .
>
