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From:   Andreas Dilger <adilger@dilger.ca>
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Subject: Re: [PATCH 3/4] ext4: indicate via a block bitmap read is prefetched
 via a tracepoint
Date:   Tue, 21 Jul 2020 01:51:56 -0600
In-Reply-To: <20200717155352.1053040-4-tytso@mit.edu>
Cc:     Ext4 Developers List <linux-ext4@vger.kernel.org>,
        Alex Zhuravlev <bzzz@whamcloud.com>
To:     Theodore Ts'o <tytso@mit.edu>
References: <20200717155352.1053040-1-tytso@mit.edu>
 <20200717155352.1053040-4-tytso@mit.edu>
Sender: linux-ext4-owner@vger.kernel.org
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On Jul 17, 2020, at 9:53 AM, Theodore Ts'o <tytso@mit.edu> wrote:
>=20
> Modify the ext4_read_block_bitmap_load tracepoint so that it tells us
> whether a block bitmap is being prefetched.
>=20
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>

I can't really say I know much about tracepoints, but the changes
look fine compared to other ext4 tracepoints.

Reviewed-by: Andreas Dilger <adilger@dilger.ca>

> ---
> fs/ext4/balloc.c            |  2 +-
> include/trace/events/ext4.h | 24 ++++++++++++++++++++----
> 2 files changed, 21 insertions(+), 5 deletions(-)
>=20
> diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
> index aaa9ec5212c8..5a2f8837200c 100644
> --- a/fs/ext4/balloc.c
> +++ b/fs/ext4/balloc.c
> @@ -494,7 +494,7 @@ ext4_read_block_bitmap_nowait(struct super_block =
*sb, ext4_group_t block_group,
> 	 * submit the buffer_head for reading
> 	 */
> 	set_buffer_new(bh);
> -	trace_ext4_read_block_bitmap_load(sb, block_group);
> +	trace_ext4_read_block_bitmap_load(sb, block_group, =
ignore_locked);
> 	bh->b_end_io =3D ext4_end_bitmap_read;
> 	get_bh(bh);
> 	submit_bh(REQ_OP_READ, REQ_META | REQ_PRIO |
> diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
> index cc41d692ae8e..cbcd2e1a608d 100644
> --- a/include/trace/events/ext4.h
> +++ b/include/trace/events/ext4.h
> @@ -1312,18 +1312,34 @@ DEFINE_EVENT(ext4__bitmap_load, =
ext4_mb_buddy_bitmap_load,
> 	TP_ARGS(sb, group)
> );
>=20
> -DEFINE_EVENT(ext4__bitmap_load, ext4_read_block_bitmap_load,
> +DEFINE_EVENT(ext4__bitmap_load, ext4_load_inode_bitmap,
>=20
> 	TP_PROTO(struct super_block *sb, unsigned long group),
>=20
> 	TP_ARGS(sb, group)
> );
>=20
> -DEFINE_EVENT(ext4__bitmap_load, ext4_load_inode_bitmap,
> +TRACE_EVENT(ext4_read_block_bitmap_load,
> +	TP_PROTO(struct super_block *sb, unsigned long group, bool =
prefetch),
>=20
> -	TP_PROTO(struct super_block *sb, unsigned long group),
> +	TP_ARGS(sb, group, prefetch),
>=20
> -	TP_ARGS(sb, group)
> +	TP_STRUCT__entry(
> +		__field(	dev_t,	dev			)
> +		__field(	__u32,	group			)
> +		__field(	bool,	prefetch		)
> +
> +	),
> +
> +	TP_fast_assign(
> +		__entry->dev	=3D sb->s_dev;
> +		__entry->group	=3D group;
> +		__entry->prefetch =3D prefetch;
> +	),
> +
> +	TP_printk("dev %d,%d group %u prefetch %d",
> +		  MAJOR(__entry->dev), MINOR(__entry->dev),
> +		  __entry->group, __entry->prefetch)
> );
>=20
> TRACE_EVENT(ext4_direct_IO_enter,
> --
> 2.24.1
>=20


Cheers, Andreas


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