Re: [PATCH] f2fs: avoid unnecessary fg_gc

[Hou Pengyang <houpengyang@huawei.com>]

On 2017/2/25 10:07, Jaegeuk Kim wrote:
> On 02/25, Hou Pengyang wrote:
>> On 2017/2/24 18:28, Chao Yu wrote:
>>> On 2017/2/24 18:01, Hou Pengyang wrote:
>>>> Under scenerio with large number of dirty nodes, and these nodes are flushed
>>>> in SSR mode during cp. enough free segemts now, no need to do fggc.
>>>
>>> We'd better break out of GC flow once we encounter cp error, so additional
>>> condition judgment is not needed.
>>>
>>
>> In (ret || !has_not_enough_free_secs(sbi, sec_freed, 0)),
>> if cp return error(NOT zero), flow will goto stop directly without
>> has_not_enough_free_secs checking;
>> if cp return ok(zero), has_not_enough_free_secs would be checked.
>
> Well, I think it'd be fine to do one gc by a background thread.
>
Currently we decide whether convert a bggc to fggc by:

if (gc_type == BG_GC && has_not_enough_free_secs(sbi, sec_freed, 0)) { 

          gc_type = FG_GC;

So how about move up write_checkpoint before gc_type = FG_GC, like:

if (gc_type == BG_GC && has_not_enough_free_secs(sbi, sec_freed, 0)) {
          write_checkpoint;
	 if still has_not_enough_free_secs:
               gc_type = FG_GC;
          else
               stay BG_GC;

Thanks,

> Thanks,
>
>>
>> Thanks,
>>
>>> Thanks,
>>>
>>>>
>>>> Signed-off-by: Hou Pengyang <houpengyang@huawei.com>
>>>> ---
>>>>    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 6c996e3..41bdfb7 100644
>>>> --- a/fs/f2fs/gc.c
>>>> +++ b/fs/f2fs/gc.c
>>>> @@ -959,7 +959,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync, bool background)
>>>>    		 * garbage collections.
>>>>    		 */
>>>>    		ret = write_checkpoint(sbi, &cpc);
>>>> -		if (ret)
>>>> +		if (ret || !has_not_enough_free_secs(sbi, sec_freed, 0))
>>>>    			goto stop;
>>>>    	} else if (gc_type == BG_GC && !background) {
>>>>    		/* f2fs_balance_fs doesn't need to do BG_GC in critical path. */
>>>>
>>>
>>>
>>> .
>>>
>>
>
> .
>



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