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

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Date:   Thu, 30 Nov 2017 23:28:20 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     Hyunchul Lee <hyc.lee@...il.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

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?

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