linux-kernel - Re: [PATCH v3] f2fs: introduce discard_io_aware

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Date:   Wed, 11 Jan 2023 21:55:37 +0800
From:   Chao Yu <chao@...nel.org>
To:     Yangtao Li <frank.li@...o.com>, jaegeuk@...nel.org
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] f2fs: introduce discard_io_aware_gran sysfs node

On 2023/1/4 19:40, Yangtao Li wrote:
> The current discard_io_aware_gran is a fixed value, change it to be
> configurable through the sys node.
> 
> Signed-off-by: Yangtao Li <frank.li@...o.com>
> ---
> v3: remove DEFAULT_IO_AWARE_DISCARD_GRANULARITY
>   Documentation/ABI/testing/sysfs-fs-f2fs |  9 +++++++++
>   fs/f2fs/f2fs.h                          |  1 +
>   fs/f2fs/segment.c                       |  3 ++-
>   fs/f2fs/sysfs.c                         | 13 +++++++++++++
>   4 files changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> index aaa379bb8a8f..75420c242cc4 100644
> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> @@ -708,3 +708,12 @@ Description:	Support configuring fault injection type, should be
>   		FAULT_LOCK_OP            0x000020000
>   		FAULT_BLKADDR            0x000040000
>   		===================      ===========
> +
> +What:		/sys/fs/f2fs/<disk>/discard_io_aware_gran
> +Date:		January 2023
> +Contact:	"Yangtao Li" <frank.li@...o.com>
> +Description:	Controls background discard granularity of inner discard thread
> +		when is not in idle. Inner thread will not issue discards with size that
> +		is smaller than granularity. The unit size is one block(4KB), now only
> +		support configuring in range of [0, 512].
> +		Default: 512

How about appending below comments to descirbe the semantics for two
special value.

By default, the value is 512, all discard IOs will be interrupted
by other inflight IO; it can be set to 0, then IO aware functionality
will be disabled.

Thanks,

> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 0a24447472db..cf60221d084e 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -409,6 +409,7 @@ 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_io_aware_gran; /* minimum discard granularity not be aware of I/O */
>   	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 */
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 34e9dc4df5bb..d988d83108b2 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -1059,7 +1059,7 @@ static void __init_discard_policy(struct f2fs_sb_info *sbi,
>   	dpolicy->granularity = granularity;
>   
>   	dpolicy->max_requests = dcc->max_discard_request;
> -	dpolicy->io_aware_gran = MAX_PLIST_NUM;
> +	dpolicy->io_aware_gran = dcc->discard_io_aware_gran;
>   	dpolicy->timeout = false;
>   
>   	if (discard_type == DPOLICY_BG) {
> @@ -2063,6 +2063,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>   	if (!dcc)
>   		return -ENOMEM;
>   
> +	dcc->discard_io_aware_gran = MAX_PLIST_NUM;
>   	dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
>   	dcc->max_ordered_discard = DEFAULT_MAX_ORDERED_DISCARD_GRANULARITY;
>   	if (F2FS_OPTION(sbi).discard_unit == DISCARD_UNIT_SEGMENT)
> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> index 805b632a3af0..e396851a6dd1 100644
> --- a/fs/f2fs/sysfs.c
> +++ b/fs/f2fs/sysfs.c
> @@ -473,6 +473,17 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
>   		return count;
>   	}
>   
> +	if (!strcmp(a->attr.name, "discard_io_aware_gran")) {
> +		if (t > MAX_PLIST_NUM)
> +			return -EINVAL;
> +		if (!f2fs_block_unit_discard(sbi))
> +			return -EINVAL;
> +		if (t == *ui)
> +			return count;
> +		*ui = t;
> +		return count;
> +	}
> +
>   	if (!strcmp(a->attr.name, "discard_granularity")) {
>   		if (t == 0 || t > MAX_PLIST_NUM)
>   			return -EINVAL;
> @@ -825,6 +836,7 @@ 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_io_aware_gran, discard_io_aware_gran);
>   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);
> @@ -960,6 +972,7 @@ 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_io_aware_gran),
>   	ATTR_LIST(discard_urgent_util),
>   	ATTR_LIST(discard_granularity),
>   	ATTR_LIST(max_ordered_discard),