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Date:   Tue, 11 Sep 2018 15:09:58 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <chao@kernel.org>
Cc:     Sahitya Tummala <stummala@codeaurora.org>,
        Chao Yu <yuchao0@huawei.com>,
        linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
Subject: Re: [f2fs-dev] [PATCH v2] f2fs: add new idle interval timing for
 discard and gc paths
Message-ID: <20180911220958.GC55456@jaegeuk-macbookpro.roam.corp.google.com>
References: <1536551252-24256-1-git-send-email-stummala@codeaurora.org>
 <5d74d46b-8141-f048-9c0a-459c82b2c449@kernel.org>
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On 09/11, Chao Yu wrote:
> On 2018/9/10 11:47, Sahitya Tummala wrote:
> > This helps to control the frequency of submission of discard and
> > GC requests independently, based on the need. The sleep timing of
> > GC thread is now aligned with this idle time when the dev is busy,
> > to avoid unnecessary periodic wakeups.
> > 
> > Suggested-by: Chao Yu <yuchao0@huawei.com>
> > Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
> > ---
> > v2:
> > -fix __issue_discard_cmd_orderly() path
> > 
> >  Documentation/ABI/testing/sysfs-fs-f2fs | 17 ++++++++++++++++-
> >  fs/f2fs/f2fs.h                          | 31 +++++++++++++++++++++++++++----
> >  fs/f2fs/gc.c                            |  6 ++++--
> >  fs/f2fs/segment.c                       | 16 ++++++----------
> >  fs/f2fs/super.c                         |  2 ++
> >  fs/f2fs/sysfs.c                         |  5 +++++
> >  6 files changed, 60 insertions(+), 17 deletions(-)
> > 
> > diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> > index 94a24ae..3ac4177 100644
> > --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> > +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> > @@ -121,7 +121,22 @@ What:		/sys/fs/f2fs/<disk>/idle_interval
> >  Date:		January 2016
> >  Contact:	"Jaegeuk Kim" <jaegeuk@kernel.org>
> >  Description:
> > -		 Controls the idle timing.
> > +		 Controls the idle timing for all paths other than
> > +		 discard and gc path.
> > +
> > +What:		/sys/fs/f2fs/<disk>/discard_idle_interval
> > +Date:		September 2018
> > +Contact:	"Chao Yu" <yuchao0@huawei.com>
> > +Contact:	"Sahitya Tummala" <stummala@codeaurora.org>
> > +Description:
> > +		 Controls the idle timing for discard path.
> > +
> > +What:		/sys/fs/f2fs/<disk>/gc_idle_interval
> > +Date:		September 2018
> > +Contact:	"Chao Yu" <yuchao0@huawei.com>
> > +Contact:	"Sahitya Tummala" <stummala@codeaurora.org>
> > +Description:
> > +		 Controls the idle timing for gc path.
> >  
> >  What:		/sys/fs/f2fs/<disk>/iostat_enable
> >  Date:		August 2017
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index abf9256..6070681 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -1093,6 +1093,8 @@ enum {
> >  enum {
> >  	CP_TIME,
> >  	REQ_TIME,
> > +	DISCARD_TIME,
> > +	GC_TIME,
> >  	MAX_TIME,
> >  };
> >  
> > @@ -1347,14 +1349,35 @@ static inline void f2fs_update_time(struct f2fs_sb_info *sbi, int type)
> >  	sbi->last_time[type] = jiffies;
> >  }
> >  
> > -static inline bool f2fs_time_over(struct f2fs_sb_info *sbi, int type)
> > +static inline bool f2fs_time_over_cp(struct f2fs_sb_info *sbi)

I don't see why we need this separately.

> > +{
> > +	unsigned long interval = sbi->interval_time[CP_TIME] * HZ;
> > +
> > +	return time_after(jiffies, sbi->last_time[CP_TIME] + interval);
> > +}
> > +
> > +static inline bool f2fs_time_over_req(struct f2fs_sb_info *sbi, int type)
> > +{
> > +	unsigned long interval = sbi->interval_time[type] * HZ;
> > +
> > +	return time_after(jiffies, sbi->last_time[REQ_TIME] + interval);
> > +}
> > +
> > +static inline unsigned int f2fs_get_wait_time(struct f2fs_sb_info *sbi,
> > +						int type)

f2fs_time_to_wait()?

> >  {
> >  	unsigned long interval = sbi->interval_time[type] * HZ;
> > +	unsigned int wait_ms = 0;
> > +	long delta;
> > +
> > +	delta = (sbi->last_time[REQ_TIME] + interval) - jiffies;
> > +	if (delta > 0)
> > +		wait_ms = jiffies_to_msecs(delta);
> >  
> > -	return time_after(jiffies, sbi->last_time[type] + interval);
> > +	return wait_ms;
> >  }
> >  
> > -static inline bool is_idle(struct f2fs_sb_info *sbi)
> > +static inline bool is_idle(struct f2fs_sb_info *sbi, int type)
> >  {
> >  	struct block_device *bdev = sbi->sb->s_bdev;
> >  	struct request_queue *q = bdev_get_queue(bdev);
> > @@ -1363,7 +1386,7 @@ static inline bool is_idle(struct f2fs_sb_info *sbi)
> >  	if (rl->count[BLK_RW_SYNC] || rl->count[BLK_RW_ASYNC])
> >  		return false;
> >  
> > -	return f2fs_time_over(sbi, REQ_TIME);
> > +	return f2fs_time_over_req(sbi, type);
> >  }
> >  
> >  /*
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index 5c8d004..c0bafea 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -83,8 +83,10 @@ static int gc_thread_func(void *data)
> >  		if (!mutex_trylock(&sbi->gc_mutex))
> >  			goto next;
> >  
> > -		if (!is_idle(sbi)) {
> > -			increase_sleep_time(gc_th, &wait_ms);
> > +		if (!is_idle(sbi, GC_TIME)) {
> > +			wait_ms = f2fs_get_wait_time(sbi, GC_TIME);
> 
> It seems this patch changes the method of increasing wait_ms here, if device is
> busy, we may wake up GC thread earlier than before, not sure we should do this.
> 
> To Jaegeuk, how do you think of this?

Yes, please let us discuss this in another patch.

> 
> Thanks,
> 
> > +			if (!wait_ms)
> > +				increase_sleep_time(gc_th, &wait_ms);
> >  			mutex_unlock(&sbi->gc_mutex);
> >  			goto next;
> >  		}
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index c5024f8..2d15733 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -511,7 +511,7 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi)
> >  	else
> >  		f2fs_build_free_nids(sbi, false, false);
> >  
> > -	if (!is_idle(sbi) &&
> > +	if (!is_idle(sbi, REQ_TIME) &&
> >  		(!excess_dirty_nats(sbi) && !excess_dirty_nodes(sbi)))
> >  		return;
> >  
> > @@ -521,7 +521,7 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi)
> >  			excess_prefree_segs(sbi) ||
> >  			excess_dirty_nats(sbi) ||
> >  			excess_dirty_nodes(sbi) ||
> > -			f2fs_time_over(sbi, CP_TIME)) {
> > +			f2fs_time_over_cp(sbi)) {
> >  		if (test_opt(sbi, DATA_FLUSH)) {
> >  			struct blk_plug plug;
> >  
> > @@ -1311,7 +1311,7 @@ static unsigned int __issue_discard_cmd_orderly(struct f2fs_sb_info *sbi,
> >  		if (dc->state != D_PREP)
> >  			goto next;
> >  
> > -		if (dpolicy->io_aware && !is_idle(sbi)) {
> > +		if (dpolicy->io_aware && !is_idle(sbi, DISCARD_TIME)) {
> >  			io_interrupted = true;
> >  			break;
> >  		}
> > @@ -1371,7 +1371,7 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
> >  			f2fs_bug_on(sbi, dc->state != D_PREP);
> >  
> >  			if (dpolicy->io_aware && i < dpolicy->io_aware_gran &&
> > -								!is_idle(sbi)) {
> > +						!is_idle(sbi, DISCARD_TIME)) {
> >  				io_interrupted = true;
> >  				break;
> >  			}
> > @@ -1564,8 +1564,6 @@ static int issue_discard_thread(void *data)
> >  	struct discard_policy dpolicy;
> >  	unsigned int wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
> >  	int issued;
> > -	unsigned long interval = sbi->interval_time[REQ_TIME] * HZ;
> > -	long delta;
> >  
> >  	set_freezable();
> >  
> > @@ -1602,10 +1600,8 @@ static int issue_discard_thread(void *data)
> >  			__wait_all_discard_cmd(sbi, &dpolicy);
> >  			wait_ms = dpolicy.min_interval;
> >  		} else if (issued == -1){
> > -			delta = (sbi->last_time[REQ_TIME] + interval) - jiffies;
> > -			if (delta > 0)
> > -				wait_ms = jiffies_to_msecs(delta);
> > -			else
> > +			wait_ms = f2fs_get_wait_time(sbi, DISCARD_TIME);
> > +			if (!wait_ms)
> >  				wait_ms = dpolicy.mid_interval;
> >  		} else {
> >  			wait_ms = dpolicy.max_interval;
> > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > index 896b885..1706f45 100644
> > --- a/fs/f2fs/super.c
> > +++ b/fs/f2fs/super.c
> > @@ -2423,6 +2423,8 @@ static void init_sb_info(struct f2fs_sb_info *sbi)
> >  	sbi->dir_level = DEF_DIR_LEVEL;
> >  	sbi->interval_time[CP_TIME] = DEF_CP_INTERVAL;
> >  	sbi->interval_time[REQ_TIME] = DEF_IDLE_INTERVAL;
> > +	sbi->interval_time[DISCARD_TIME] = DEF_IDLE_INTERVAL;
> > +	sbi->interval_time[GC_TIME] = DEF_IDLE_INTERVAL;
> >  	clear_sbi_flag(sbi, SBI_NEED_FSCK);
> >  
> >  	for (i = 0; i < NR_COUNT_TYPE; i++)
> > diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> > index 81c0e53..0afe99c 100644
> > --- a/fs/f2fs/sysfs.c
> > +++ b/fs/f2fs/sysfs.c
> > @@ -407,6 +407,9 @@ static ssize_t f2fs_feature_show(struct f2fs_attr *a,
> >  F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, dir_level, dir_level);
> >  F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, cp_interval, interval_time[CP_TIME]);
> >  F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, idle_interval, interval_time[REQ_TIME]);
> > +F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, discard_idle_interval,
> > +					interval_time[DISCARD_TIME]);
> > +F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, gc_idle_interval, interval_time[GC_TIME]);
> >  F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, iostat_enable, iostat_enable);
> >  F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, readdir_ra, readdir_ra);
> >  F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, gc_pin_file_thresh, gc_pin_file_threshold);
> > @@ -460,6 +463,8 @@ static ssize_t f2fs_feature_show(struct f2fs_attr *a,
> >  	ATTR_LIST(dirty_nats_ratio),
> >  	ATTR_LIST(cp_interval),
> >  	ATTR_LIST(idle_interval),
> > +	ATTR_LIST(discard_idle_interval),
> > +	ATTR_LIST(gc_idle_interval),
> >  	ATTR_LIST(iostat_enable),
> >  	ATTR_LIST(readdir_ra),
> >  	ATTR_LIST(gc_pin_file_thresh),
> >