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

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Date:   Thu, 14 Dec 2017 13:18:31 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Hyunchul Lee <hyc.lee@...il.com>
Cc:     Chao Yu <yuchao0@...wei.com>,
        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

Hello,

On 12/01, Hyunchul Lee wrote:
> 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.

Same in what way?

WRITE_LIFE_NOT_SET = 0,
WRITE_LIFE_NONE = 1,

Still, you didn't answer why we have to assign LIFE_NONE to WARM_DATA?

Thanks,

> 
> 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);
> >>>  		}
> >>>  	}
> >>>  
> >>>
> >