Re: [PATCH] f2fs: introduce discard_urgent_util sysfs node

[Chao Yu]

On 2022/11/17 22:35, Yangtao Li wrote:
> Through this node, you can control the background discard
> to run more aggressively when reach the utilization rate of
> the space.
>
> Signed-off-by: Yangtao Li <frank.li@xxxxxxxx>
> ---
>   Documentation/ABI/testing/sysfs-fs-f2fs | 8 ++++++++
>   fs/f2fs/f2fs.h                          | 1 +
>   fs/f2fs/segment.c                       | 3 ++-
>   fs/f2fs/sysfs.c                         | 9 +++++++++
>   4 files changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> index 24e7cb77f265..202ac1bfc6f2 100644
> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> @@ -646,3 +646,11 @@ Date:		October 2022
>   Contact:	"Yangtao Li" <frank.li@xxxxxxxx>
>   Description:	Show the current gc_mode as a string.
>   		This is a read-only entry.
> +
> +What:		/sys/fs/f2fs/<disk>/discard_urgent_util
> +Date:		November 2022
> +Contact:	"Yangtao Li" <frank.li@xxxxxxxx>
> +Description:	When space utilization exceeds this, do background DISCARD aggressively.
> +		Does DISCARD forcibly in a period of given min_discard_issue_time when the number
> +		of discards is not 0 and set discard granularity to 1.
> +	    Default: 80
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index dedac413bf64..fe42ac74491d 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -411,6 +411,7 @@ struct discard_cmd_control {
>   	unsigned int min_discard_issue_time;	/* min. interval between discard issue */
>   	unsigned int mid_discard_issue_time;	/* mid. interval between discard issue */
>   	unsigned int max_discard_issue_time;	/* max. interval between discard issue */
> +	unsigned int discard_urgent_util;	/* utilization which issue discard proactively */
>   	unsigned int discard_granularity;	/* discard granularity */
>   	unsigned int max_ordered_discard;	/* maximum discard granularity issued by lba order */
>   	unsigned int undiscard_blks;		/* # of undiscard blocks */
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 8b0b76550578..575c24b42df9 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -1069,7 +1069,7 @@ static void __init_discard_policy(struct f2fs_sb_info *sbi,
>   		dpolicy->io_aware = true;
>   		dpolicy->sync = false;
>   		dpolicy->ordered = true;
> -		if (utilization(sbi) > DEF_DISCARD_URGENT_UTIL) {
> +		if (utilization(sbi) > dcc->discard_urgent_util) {
>   			dpolicy->granularity = 1;
>   			if (atomic_read(&dcc->discard_cmd_cnt))
>   				dpolicy->max_interval =
> @@ -2085,6 +2085,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>   	dcc->min_discard_issue_time = DEF_MIN_DISCARD_ISSUE_TIME;
>   	dcc->mid_discard_issue_time = DEF_MID_DISCARD_ISSUE_TIME;
>   	dcc->max_discard_issue_time = DEF_MAX_DISCARD_ISSUE_TIME;
> +	dcc->discard_urgent_util = DEF_DISCARD_URGENT_UTIL;
>   	dcc->undiscard_blks = 0;
>   	dcc->next_pos = 0;
>   	dcc->root = RB_ROOT_CACHED;
> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> index 97bf0dbb0974..a7dc726054b9 100644
> --- a/fs/f2fs/sysfs.c
> +++ b/fs/f2fs/sysfs.c
> @@ -493,6 +493,13 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
>   		return count;
>   	}
>   
> +	if (!strcmp(a->attr.name, "discard_urgent_util")) {
> +		if (t == 0 || t > 100)

0 is allowed?

Thanks,

> +			return -EINVAL;
> +		*ui = t;
> +		return count;
> +	}
> +
>   	if (!strcmp(a->attr.name, "migration_granularity")) {
>   		if (t == 0 || t > sbi->segs_per_sec)
>   			return -EINVAL;
> @@ -795,6 +802,7 @@ F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_discard_request, max_discard_req
>   F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, min_discard_issue_time, min_discard_issue_time);
>   F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, mid_discard_issue_time, mid_discard_issue_time);
>   F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_discard_issue_time, max_discard_issue_time);
> +F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_urgent_util, discard_urgent_util);
>   F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
>   F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_ordered_discard, max_ordered_discard);
>   F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, reserved_blocks);
> @@ -925,6 +933,7 @@ static struct attribute *f2fs_attrs[] = {
>   	ATTR_LIST(min_discard_issue_time),
>   	ATTR_LIST(mid_discard_issue_time),
>   	ATTR_LIST(max_discard_issue_time),
> +	ATTR_LIST(discard_urgent_util),
>   	ATTR_LIST(discard_granularity),
>   	ATTR_LIST(max_ordered_discard),
>   	ATTR_LIST(pending_discard),