Re: [PATCH 41/45] xfs: support write life time based data placement

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Feb 18, 2025 at 09:10:44AM +0100, Christoph Hellwig wrote:
> From: Hans Holmberg <hans.holmberg@wdc.com>
> 
> Add a file write life time data placement allocation scheme that aims to
> minimize fragmentation and thereby to do two things:
> 
>  a) separate file data to different zones when possible.
>  b) colocate file data of similar life times when feasible.
> 
> To get best results, average file sizes should align with the zone
> capacity that is reported through the XFS_IOC_FSGEOMETRY ioctl.
> 
> This improvement in data placement efficiency reduces the number of
> blocks requiring relocation by GC, and thus decreases overall write
> amplification.  The impact on performance varies depending on how full
> the file system is.
> 
> For RocksDB using leveled compaction, the lifetime hints can improve
> throughput for overwrite workloads at 80% file system utilization by
> ~10%, but for lower file system utilization there won't be as much
> benefit in application performance as there is less need for garbage
> collection to start with.
> 
> Lifetime hints can be disabled using the nolifetime mount option.
> 
> Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

I appreciate the extra information in the commit message!
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/xfs/xfs_mount.h      |   2 +
>  fs/xfs/xfs_super.c      |  15 +++++
>  fs/xfs/xfs_zone_alloc.c | 130 +++++++++++++++++++++++++++++++++++-----
>  fs/xfs/xfs_zone_gc.c    |   4 +-
>  fs/xfs/xfs_zone_priv.h  |   9 ++-
>  5 files changed, 141 insertions(+), 19 deletions(-)
> 
> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> index 181b9bcff2cb..b34a496081db 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -373,6 +373,7 @@ typedef struct xfs_mount {
>  #define XFS_FEAT_ZONED		(1ULL << 29)	/* zoned RT device */
>  
>  /* Mount features */
> +#define XFS_FEAT_NOLIFETIME	(1ULL << 47)	/* disable lifetime hints */
>  #define XFS_FEAT_NOATTR2	(1ULL << 48)	/* disable attr2 creation */
>  #define XFS_FEAT_NOALIGN	(1ULL << 49)	/* ignore alignment */
>  #define XFS_FEAT_ALLOCSIZE	(1ULL << 50)	/* user specified allocation size */
> @@ -428,6 +429,7 @@ __XFS_HAS_FEAT(large_extent_counts, NREXT64)
>  __XFS_HAS_FEAT(exchange_range, EXCHANGE_RANGE)
>  __XFS_HAS_FEAT(metadir, METADIR)
>  __XFS_HAS_FEAT(zoned, ZONED)
> +__XFS_HAS_FEAT(nolifetime, NOLIFETIME)
>  
>  static inline bool xfs_has_rtgroups(const struct xfs_mount *mp)
>  {
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index aac50bdd629c..6ae2a3937791 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -111,6 +111,7 @@ enum {
>  	Opt_prjquota, Opt_uquota, Opt_gquota, Opt_pquota,
>  	Opt_uqnoenforce, Opt_gqnoenforce, Opt_pqnoenforce, Opt_qnoenforce,
>  	Opt_discard, Opt_nodiscard, Opt_dax, Opt_dax_enum, Opt_max_open_zones,
> +	Opt_lifetime, Opt_nolifetime,
>  };
>  
>  static const struct fs_parameter_spec xfs_fs_parameters[] = {
> @@ -156,6 +157,8 @@ static const struct fs_parameter_spec xfs_fs_parameters[] = {
>  	fsparam_flag("dax",		Opt_dax),
>  	fsparam_enum("dax",		Opt_dax_enum, dax_param_enums),
>  	fsparam_u32("max_open_zones",	Opt_max_open_zones),
> +	fsparam_flag("lifetime",	Opt_lifetime),
> +	fsparam_flag("nolifetime",	Opt_nolifetime),
>  	{}
>  };
>  
> @@ -184,6 +187,7 @@ xfs_fs_show_options(
>  		{ XFS_FEAT_LARGE_IOSIZE,	",largeio" },
>  		{ XFS_FEAT_DAX_ALWAYS,		",dax=always" },
>  		{ XFS_FEAT_DAX_NEVER,		",dax=never" },
> +		{ XFS_FEAT_NOLIFETIME,		",nolifetime" },
>  		{ 0, NULL }
>  	};
>  	struct xfs_mount	*mp = XFS_M(root->d_sb);
> @@ -1091,6 +1095,11 @@ xfs_finish_flags(
>  "max_open_zones mount option only supported on zoned file systems.");
>  			return -EINVAL;
>  		}
> +		if (mp->m_features & XFS_FEAT_NOLIFETIME) {
> +			xfs_warn(mp,
> +"nolifetime mount option only supported on zoned file systems.");
> +			return -EINVAL;
> +		}
>  	}
>  
>  	return 0;
> @@ -1478,6 +1487,12 @@ xfs_fs_parse_param(
>  	case Opt_max_open_zones:
>  		parsing_mp->m_max_open_zones = result.uint_32;
>  		return 0;
> +	case Opt_lifetime:
> +		parsing_mp->m_features &= ~XFS_FEAT_NOLIFETIME;
> +		return 0;
> +	case Opt_nolifetime:
> +		parsing_mp->m_features |= XFS_FEAT_NOLIFETIME;
> +		return 0;
>  	default:
>  		xfs_warn(parsing_mp, "unknown mount option [%s].", param->key);
>  		return -EINVAL;
> diff --git a/fs/xfs/xfs_zone_alloc.c b/fs/xfs/xfs_zone_alloc.c
> index 7537ad4c51d1..379112eebd70 100644
> --- a/fs/xfs/xfs_zone_alloc.c
> +++ b/fs/xfs/xfs_zone_alloc.c
> @@ -423,6 +423,7 @@ static struct xfs_open_zone *
>  xfs_init_open_zone(
>  	struct xfs_rtgroup	*rtg,
>  	xfs_rgblock_t		write_pointer,
> +	enum rw_hint		write_hint,
>  	bool			is_gc)
>  {
>  	struct xfs_open_zone	*oz;
> @@ -433,6 +434,7 @@ xfs_init_open_zone(
>  	oz->oz_rtg = rtg;
>  	oz->oz_write_pointer = write_pointer;
>  	oz->oz_written = write_pointer;
> +	oz->oz_write_hint = write_hint;
>  	oz->oz_is_gc = is_gc;
>  
>  	/*
> @@ -452,6 +454,7 @@ xfs_init_open_zone(
>  struct xfs_open_zone *
>  xfs_open_zone(
>  	struct xfs_mount	*mp,
> +	enum rw_hint		write_hint,
>  	bool			is_gc)
>  {
>  	struct xfs_zone_info	*zi = mp->m_zone_info;
> @@ -464,12 +467,13 @@ xfs_open_zone(
>  		return NULL;
>  
>  	set_current_state(TASK_RUNNING);
> -	return xfs_init_open_zone(to_rtg(xg), 0, is_gc);
> +	return xfs_init_open_zone(to_rtg(xg), 0, write_hint, is_gc);
>  }
>  
>  static struct xfs_open_zone *
>  xfs_try_open_zone(
> -	struct xfs_mount	*mp)
> +	struct xfs_mount	*mp,
> +	enum rw_hint		write_hint)
>  {
>  	struct xfs_zone_info	*zi = mp->m_zone_info;
>  	struct xfs_open_zone	*oz;
> @@ -486,7 +490,7 @@ xfs_try_open_zone(
>  	 */
>  	zi->zi_nr_open_zones++;
>  	spin_unlock(&zi->zi_open_zones_lock);
> -	oz = xfs_open_zone(mp, false);
> +	oz = xfs_open_zone(mp, write_hint, false);
>  	spin_lock(&zi->zi_open_zones_lock);
>  	if (!oz) {
>  		zi->zi_nr_open_zones--;
> @@ -509,16 +513,78 @@ xfs_try_open_zone(
>  	return oz;
>  }
>  
> +/*
> + * For data with short or medium lifetime, try to colocated it into an
> + * already open zone with a matching temperature.
> + */
> +static bool
> +xfs_colocate_eagerly(
> +	enum rw_hint		file_hint)
> +{
> +	switch (file_hint) {
> +	case WRITE_LIFE_MEDIUM:
> +	case WRITE_LIFE_SHORT:
> +	case WRITE_LIFE_NONE:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static bool
> +xfs_good_hint_match(
> +	struct xfs_open_zone	*oz,
> +	enum rw_hint		file_hint)
> +{
> +	switch (oz->oz_write_hint) {
> +	case WRITE_LIFE_LONG:
> +	case WRITE_LIFE_EXTREME:
> +		/* colocate long and extreme */
> +		if (file_hint == WRITE_LIFE_LONG ||
> +		    file_hint == WRITE_LIFE_EXTREME)
> +			return true;
> +		break;
> +	case WRITE_LIFE_MEDIUM:
> +		/* colocate medium with medium */
> +		if (file_hint == WRITE_LIFE_MEDIUM)
> +			return true;
> +		break;
> +	case WRITE_LIFE_SHORT:
> +	case WRITE_LIFE_NONE:
> +	case WRITE_LIFE_NOT_SET:
> +		/* colocate short and none */
> +		if (file_hint <= WRITE_LIFE_SHORT)
> +			return true;
> +		break;
> +	}
> +	return false;
> +}
> +
>  static bool
>  xfs_try_use_zone(
>  	struct xfs_zone_info	*zi,
> -	struct xfs_open_zone	*oz)
> +	enum rw_hint		file_hint,
> +	struct xfs_open_zone	*oz,
> +	bool			lowspace)
>  {
>  	if (oz->oz_write_pointer == rtg_blocks(oz->oz_rtg))
>  		return false;
> +	if (!lowspace && !xfs_good_hint_match(oz, file_hint))
> +		return false;
>  	if (!atomic_inc_not_zero(&oz->oz_ref))
>  		return false;
>  
> +	/*
> +	 * If we have a hint set for the data, use that for the zone even if
> +	 * some data was written already without any hint set, but don't change
> +	 * the temperature after that as that would make little sense without
> +	 * tracking per-temperature class written block counts, which is
> +	 * probably overkill anyway.
> +	 */
> +	if (file_hint != WRITE_LIFE_NOT_SET &&
> +	    oz->oz_write_hint == WRITE_LIFE_NOT_SET)
> +		oz->oz_write_hint = file_hint;
> +
>  	/*
>  	 * If we couldn't match by inode or life time we just pick the first
>  	 * zone with enough space above.  For that we want the least busy zone
> @@ -533,14 +599,16 @@ xfs_try_use_zone(
>  
>  static struct xfs_open_zone *
>  xfs_select_open_zone_lru(
> -	struct xfs_zone_info	*zi)
> +	struct xfs_zone_info	*zi,
> +	enum rw_hint		file_hint,
> +	bool			lowspace)
>  {
>  	struct xfs_open_zone	*oz;
>  
>  	lockdep_assert_held(&zi->zi_open_zones_lock);
>  
>  	list_for_each_entry(oz, &zi->zi_open_zones, oz_entry)
> -		if (xfs_try_use_zone(zi, oz))
> +		if (xfs_try_use_zone(zi, file_hint, oz, lowspace))
>  			return oz;
>  
>  	cond_resched_lock(&zi->zi_open_zones_lock);
> @@ -549,20 +617,28 @@ xfs_select_open_zone_lru(
>  
>  static struct xfs_open_zone *
>  xfs_select_open_zone_mru(
> -	struct xfs_zone_info	*zi)
> +	struct xfs_zone_info	*zi,
> +	enum rw_hint		file_hint)
>  {
>  	struct xfs_open_zone	*oz;
>  
>  	lockdep_assert_held(&zi->zi_open_zones_lock);
>  
>  	list_for_each_entry_reverse(oz, &zi->zi_open_zones, oz_entry)
> -		if (xfs_try_use_zone(zi, oz))
> +		if (xfs_try_use_zone(zi, file_hint, oz, false))
>  			return oz;
>  
>  	cond_resched_lock(&zi->zi_open_zones_lock);
>  	return NULL;
>  }
>  
> +static inline enum rw_hint xfs_inode_write_hint(struct xfs_inode *ip)
> +{
> +	if (xfs_has_nolifetime(ip->i_mount))
> +		return WRITE_LIFE_NOT_SET;
> +	return VFS_I(ip)->i_write_hint;
> +}
> +
>  /*
>   * Try to pack inodes that are written back after they were closed tight instead
>   * of trying to open new zones for them or spread them to the least recently
> @@ -586,6 +662,7 @@ static inline bool xfs_zoned_pack_tight(struct xfs_inode *ip)
>  static struct xfs_open_zone *
>  xfs_select_zone_nowait(
>  	struct xfs_mount	*mp,
> +	enum rw_hint		write_hint,
>  	bool			pack_tight)
>  {
>  	struct xfs_zone_info	*zi = mp->m_zone_info;
> @@ -594,20 +671,38 @@ xfs_select_zone_nowait(
>  	if (xfs_is_shutdown(mp))
>  		return NULL;
>  
> +	/*
> +	 * Try to fill up open zones with matching temperature if available.  It
> +	 * is better to try to co-locate data when this is favorable, so we can
> +	 * activate empty zones when it is statistically better to separate
> +	 * data.
> +	 */
>  	spin_lock(&zi->zi_open_zones_lock);
> -	if (pack_tight)
> -		oz = xfs_select_open_zone_mru(zi);
> +	if (xfs_colocate_eagerly(write_hint))
> +		oz = xfs_select_open_zone_lru(zi, write_hint, false);
> +	else if (pack_tight)
> +		oz = xfs_select_open_zone_mru(zi, write_hint);
>  	if (oz)
>  		goto out_unlock;
>  
>  	/*
>  	 * See if we can open a new zone and use that.
>  	 */
> -	oz = xfs_try_open_zone(mp);
> +	oz = xfs_try_open_zone(mp, write_hint);
>  	if (oz)
>  		goto out_unlock;
>  
> -	oz = xfs_select_open_zone_lru(zi);
> +	/*
> +	 * Try to colocate cold data with other cold data if we failed to open a
> +	 * new zone for it.
> +	 */
> +	if (write_hint != WRITE_LIFE_NOT_SET &&
> +	    !xfs_colocate_eagerly(write_hint))
> +		oz = xfs_select_open_zone_lru(zi, write_hint, false);
> +	if (!oz)
> +		oz = xfs_select_open_zone_lru(zi, WRITE_LIFE_NOT_SET, false);
> +	if (!oz)
> +		oz = xfs_select_open_zone_lru(zi, WRITE_LIFE_NOT_SET, true);
>  out_unlock:
>  	spin_unlock(&zi->zi_open_zones_lock);
>  	return oz;
> @@ -616,19 +711,20 @@ xfs_select_zone_nowait(
>  static struct xfs_open_zone *
>  xfs_select_zone(
>  	struct xfs_mount	*mp,
> +	enum rw_hint		write_hint,
>  	bool			pack_tight)
>  {
>  	struct xfs_zone_info	*zi = mp->m_zone_info;
>  	DEFINE_WAIT		(wait);
>  	struct xfs_open_zone	*oz;
>  
> -	oz = xfs_select_zone_nowait(mp, pack_tight);
> +	oz = xfs_select_zone_nowait(mp, write_hint, pack_tight);
>  	if (oz)
>  		return oz;
>  
>  	for (;;) {
>  		prepare_to_wait(&zi->zi_zone_wait, &wait, TASK_UNINTERRUPTIBLE);
> -		oz = xfs_select_zone_nowait(mp, pack_tight);
> +		oz = xfs_select_zone_nowait(mp, write_hint, pack_tight);
>  		if (oz)
>  			break;
>  		schedule();
> @@ -706,6 +802,7 @@ xfs_zone_alloc_and_submit(
>  {
>  	struct xfs_inode	*ip = XFS_I(ioend->io_inode);
>  	struct xfs_mount	*mp = ip->i_mount;
> +	enum rw_hint		write_hint = xfs_inode_write_hint(ip);
>  	bool			pack_tight = xfs_zoned_pack_tight(ip);
>  	unsigned int		alloc_len;
>  	struct iomap_ioend	*split;
> @@ -723,7 +820,7 @@ xfs_zone_alloc_and_submit(
>  		*oz = xfs_last_used_zone(ioend);
>  	if (!*oz) {
>  select_zone:
> -		*oz = xfs_select_zone(mp, pack_tight);
> +		*oz = xfs_select_zone(mp, write_hint, pack_tight);
>  		if (!*oz)
>  			goto out_error;
>  	}
> @@ -861,7 +958,8 @@ xfs_init_zone(
>  		struct xfs_open_zone *oz;
>  
>  		atomic_inc(&rtg_group(rtg)->xg_active_ref);
> -		oz = xfs_init_open_zone(rtg, write_pointer, false);
> +		oz = xfs_init_open_zone(rtg, write_pointer, WRITE_LIFE_NOT_SET,
> +				false);
>  		list_add_tail(&oz->oz_entry, &zi->zi_open_zones);
>  		zi->zi_nr_open_zones++;
>  
> diff --git a/fs/xfs/xfs_zone_gc.c b/fs/xfs/xfs_zone_gc.c
> index 0e1c39f2aaba..c5136ea9bb1d 100644
> --- a/fs/xfs/xfs_zone_gc.c
> +++ b/fs/xfs/xfs_zone_gc.c
> @@ -547,7 +547,7 @@ xfs_zone_gc_select_target(
>  
>  	ASSERT(zi->zi_nr_open_zones <=
>  		mp->m_max_open_zones - XFS_OPEN_GC_ZONES);
> -	oz = xfs_open_zone(mp, true);
> +	oz = xfs_open_zone(mp, WRITE_LIFE_NOT_SET, true);
>  	if (oz)
>  		trace_xfs_zone_gc_target_opened(oz->oz_rtg);
>  	spin_lock(&zi->zi_open_zones_lock);
> @@ -1117,7 +1117,7 @@ xfs_zone_gc_mount(
>  	    zi->zi_nr_open_zones == mp->m_max_open_zones)
>  		oz = xfs_zone_gc_steal_open(zi);
>  	else
> -		oz = xfs_open_zone(mp, true);
> +		oz = xfs_open_zone(mp, WRITE_LIFE_NOT_SET, true);
>  	if (!oz) {
>  		xfs_warn(mp, "unable to allocate a zone for gc");
>  		error = -EIO;
> diff --git a/fs/xfs/xfs_zone_priv.h b/fs/xfs/xfs_zone_priv.h
> index f6c76d751a49..ab696975a993 100644
> --- a/fs/xfs/xfs_zone_priv.h
> +++ b/fs/xfs/xfs_zone_priv.h
> @@ -26,6 +26,12 @@ struct xfs_open_zone {
>  	 */
>  	xfs_rgblock_t		oz_written;
>  
> +	/*
> +	 * Write hint (data temperature) assigned to this zone, or
> +	 * WRITE_LIFE_NOT_SET if none was set.
> +	 */
> +	enum rw_hint		oz_write_hint;
> +
>  	/*
>  	 * Is this open zone used for garbage collection?  There can only be a
>  	 * single open GC zone, which is pointed to by zi_open_gc_zone in
> @@ -100,7 +106,8 @@ struct xfs_zone_info {
>  
>  };
>  
> -struct xfs_open_zone *xfs_open_zone(struct xfs_mount *mp, bool is_gc);
> +struct xfs_open_zone *xfs_open_zone(struct xfs_mount *mp,
> +		enum rw_hint write_hint, bool is_gc);
>  
>  int xfs_zone_gc_reset_sync(struct xfs_rtgroup *rtg);
>  bool xfs_zoned_need_gc(struct xfs_mount *mp);
> -- 
> 2.45.2
> 
>