linux-ext4 - Re: [PATCH 3/4] ext4: indicate via a block bitmap read is prefetched via a tracepoint

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Message-Id: <98AFEBD1-81E5-42ED-8851-4FA5FF3C62F1@dilger.ca>
Date:   Tue, 21 Jul 2020 01:51:56 -0600
From:   Andreas Dilger <adilger@...ger.ca>
To:     Theodore Ts'o <tytso@....edu>
Cc:     Ext4 Developers List <linux-ext4@...r.kernel.org>,
        Alex Zhuravlev <bzzz@...mcloud.com>
Subject: Re: [PATCH 3/4] ext4: indicate via a block bitmap read is prefetched
 via a tracepoint

On Jul 17, 2020, at 9:53 AM, Theodore Ts'o <tytso@....edu> wrote:
> 
> Modify the ext4_read_block_bitmap_load tracepoint so that it tells us
> whether a block bitmap is being prefetched.
> 
> Signed-off-by: Theodore Ts'o <tytso@....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@...ger.ca>

> ---
> fs/ext4/balloc.c            |  2 +-
> include/trace/events/ext4.h | 24 ++++++++++++++++++++----
> 2 files changed, 21 insertions(+), 5 deletions(-)
> 
> 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 = 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)
> );
> 
> -DEFINE_EVENT(ext4__bitmap_load, ext4_read_block_bitmap_load,
> +DEFINE_EVENT(ext4__bitmap_load, ext4_load_inode_bitmap,
> 
> 	TP_PROTO(struct super_block *sb, unsigned long group),
> 
> 	TP_ARGS(sb, group)
> );
> 
> -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),
> 
> -	TP_PROTO(struct super_block *sb, unsigned long group),
> +	TP_ARGS(sb, group, prefetch),
> 
> -	TP_ARGS(sb, group)
> +	TP_STRUCT__entry(
> +		__field(	dev_t,	dev			)
> +		__field(	__u32,	group			)
> +		__field(	bool,	prefetch		)
> +
> +	),
> +
> +	TP_fast_assign(
> +		__entry->dev	= sb->s_dev;
> +		__entry->group	= group;
> +		__entry->prefetch = prefetch;
> +	),
> +
> +	TP_printk("dev %d,%d group %u prefetch %d",
> +		  MAJOR(__entry->dev), MINOR(__entry->dev),
> +		  __entry->group, __entry->prefetch)
> );
> 
> TRACE_EVENT(ext4_direct_IO_enter,
> --
> 2.24.1
> 


Cheers, Andreas






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