linux-kernel - Re: [PATCH 1/2] f2fs: pass down write hints to block layer for bufferd write

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Date:   Fri, 01 Dec 2017 17:50:11 +0900
From:   Hyunchul Lee <hyc.lee@...il.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <yuchao0@...wei.com>
CC:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        kernel-team@....com, Jens Axboe <axboe@...nel.dk>,
        Hyunchul Lee <cheol.lee@....com>
Subject: Re: [PATCH 1/2] f2fs: pass down write hints to block layer for bufferd
 write

Hi Jaegeuk,

On 12/01/2017 04:28 PM, Jaegeuk Kim wrote:
> On 11/30, Chao Yu wrote:
>> On 2017/11/28 8:23, Hyunchul Lee wrote:
>>> From: Hyunchul Lee <cheol.lee@....com>
>>>
>>> This implements which hint is passed down to block layer
>>> for datas from the specific segment type.
>>>
>>> segment type                     hints
>>> ------------                     -----
>>> COLD_NODE & COLD_DATA            WRITE_LIFE_EXTREME
>>> WARM_DATA                        WRITE_LIFE_NONE
>>> HOT_NODE & WARM_NODE             WRITE_LIFE_LONG
>>> HOT_DATA                         WRITE_LIFE_MEDIUM
>>> META_DATA                        WRITE_LIFE_SHORT
>>
>> The correspondence looks good to me.
> 
> Still, I don't fully get the point. Why do we have to assign WRITE_LIFE_NONE
> to WARM_DATA? Why not using WRITE_LIFE_NOT_SET?
> 

I think LIFE_NONE and LIFE_NOT_SET are the same. So I chose LIFE_NONE simply.

Thanks.

>>>
>>> Many thanks to Chao Yu and Jaegeuk Kim for comments to
>>> implement this patch.
>>>
>>> Signed-off-by: Hyunchul Lee <cheol.lee@....com>
>>> ---
>>>  fs/f2fs/data.c    |  1 +
>>>  fs/f2fs/f2fs.h    |  2 ++
>>>  fs/f2fs/segment.c | 29 +++++++++++++++++++++++++++++
>>>  fs/f2fs/super.c   |  2 ++
>>>  4 files changed, 34 insertions(+)
>>>
>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>> index a7ae418..0919a43 100644
>>> --- a/fs/f2fs/data.c
>>> +++ b/fs/f2fs/data.c
>>> @@ -437,6 +437,7 @@ int f2fs_submit_page_write(struct f2fs_io_info *fio)
>>>  		}
>>>  		io->bio = __bio_alloc(sbi, fio->new_blkaddr,
>>>  						BIO_MAX_PAGES, false);
>>> +		io->bio->bi_write_hint = io->write_hint;
>>
>> Need to assign bi_write_hint for IPU path?
>>
>> - rewrite_data_page
>>  - f2fs_submit_page_bio
>>
>>>  		io->fio = *fio;
>>>  	}
>>>  
>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>> index 7bcd148..be3cb0c 100644
>>> --- a/fs/f2fs/f2fs.h
>>> +++ b/fs/f2fs/f2fs.h
>>> @@ -969,6 +969,7 @@ struct f2fs_bio_info {
>>>  	struct rw_semaphore io_rwsem;	/* blocking op for bio */
>>>  	spinlock_t io_lock;		/* serialize DATA/NODE IOs */
>>>  	struct list_head io_list;	/* track fios */
>>> +	enum rw_hint write_hint;
>>
>> Add missing comment?
>>
>>>  };
>>>  
>>>  #define FDEV(i)				(sbi->devs[i])
>>> @@ -2674,6 +2675,7 @@ int lookup_journal_in_cursum(struct f2fs_journal *journal, int type,
>>>  int __init create_segment_manager_caches(void);
>>>  void destroy_segment_manager_caches(void);
>>>  int rw_hint_to_seg_type(enum rw_hint hint);
>>> +enum rw_hint io_type_to_rw_hint(enum page_type page, enum temp_type temp);
>>>  
>>>  /*
>>>   * checkpoint.c
>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>> index c117e09..0570db7 100644
>>> --- a/fs/f2fs/segment.c
>>> +++ b/fs/f2fs/segment.c
>>> @@ -2446,6 +2446,35 @@ int rw_hint_to_seg_type(enum rw_hint hint)
>>>  	}
>>>  }
>>>  
>>
>> It will be better to copy commit log here to declare correspondence
>> more clearly.
>>
>> Thanks,
>>
>>> +enum rw_hint io_type_to_rw_hint(enum page_type page, enum temp_type temp)
>>> +{
>>> +	if (page == DATA) {
>>> +		switch (temp) {
>>> +		case WARM:
>>> +			return WRITE_LIFE_NONE;
>>> +		case COLD:
>>> +			return WRITE_LIFE_EXTREME;
>>> +		case HOT:
>>> +			return WRITE_LIFE_MEDIUM;
>>> +		default:
>>> +			return WRITE_LIFE_NOT_SET;
>>> +		}
>>> +	} else if (page == NODE) {
>>> +		switch (temp) {
>>> +		case WARM:
>>> +		case HOT:
>>> +			return WRITE_LIFE_LONG;
>>> +		case COLD:
>>> +			return WRITE_LIFE_EXTREME;
>>> +		default:
>>> +			return WRITE_LIFE_NOT_SET;
>>> +		}
>>> +
>>> +	} else {
>>> +		return WRITE_LIFE_SHORT;
>>> +	}
>>> +}
>>> +
>>>  static int __get_segment_type_2(struct f2fs_io_info *fio)
>>>  {
>>>  	if (fio->type == DATA)
>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>> index a6c5dd4..51c19a0 100644
>>> --- a/fs/f2fs/super.c
>>> +++ b/fs/f2fs/super.c
>>> @@ -2508,6 +2508,8 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>>  			sbi->write_io[i][j].bio = NULL;
>>>  			spin_lock_init(&sbi->write_io[i][j].io_lock);
>>>  			INIT_LIST_HEAD(&sbi->write_io[i][j].io_list);
>>> +			sbi->write_io[i][j].write_hint =
>>> +						io_type_to_rw_hint(i, j);
>>>  		}
>>>  	}
>>>  
>>>
>