linux-kernel - Re: [PATCH v2 2/2] mm: mmap_lock: use DECLARE_EVENT_CLASS and DEFINE_EVENT

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Message-ID: <9eede0f3-cc9e-753b-16f1-0f5c3ad57794@suse.cz>
Date:   Mon, 11 Oct 2021 10:02:42 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Gang Li <ligang.bdlg@...edance.com>, rostedt@...dmis.org
Cc:     mingo@...hat.com, akpm@...ux-foundation.org,
        axelrasmussen@...gle.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v2 2/2] mm: mmap_lock: use DECLARE_EVENT_CLASS and
 DEFINE_EVENT_FN

On 10/9/21 09:12, Gang Li wrote:
> By using DECLARE_EVENT_CLASS and TRACE_EVENT_FN, we can save a lot
> of space from duplicate code.
> 
> Signed-off-by: Gang Li <ligang.bdlg@...edance.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> @@ -36,11 +36,19 @@ TRACE_EVENT_FN(mmap_lock_start_locking,
>  		__entry->mm,
>  		__get_str(memcg_path),
>  		__entry->write ? "true" : "false"
> -	),
> -
> -	trace_mmap_lock_reg, trace_mmap_lock_unreg
> +	)
>  );
>  
> +#define DEFINE_MMAP_LOCK_EVENT(name)                                    \
> +	DEFINE_EVENT_FN(mmap_lock, name,                                \
> +		TP_PROTO(struct mm_struct *mm, const char *memcg_path,  \
> +			bool write),                                    \
> +		TP_ARGS(mm, memcg_path, write),                         \
> +		trace_mmap_lock_reg, trace_mmap_lock_unreg)

A question (for Steven). I've several times wondered why DEFINE_EVENT has to
pass TP_PROTO/TP_ARGS even if they are often the same. Is it not possible to
have a variant that doesn't need that, and thus also doesn't need such extra
wrapping as above?

> +
> +DEFINE_MMAP_LOCK_EVENT(mmap_lock_start_locking);
> +DEFINE_MMAP_LOCK_EVENT(mmap_lock_released);
> +
>  TRACE_EVENT_FN(mmap_lock_acquire_returned,
>  
>  	TP_PROTO(struct mm_struct *mm, const char *memcg_path, bool write,
> @@ -73,34 +81,6 @@ TRACE_EVENT_FN(mmap_lock_acquire_returned,
>  	trace_mmap_lock_reg, trace_mmap_lock_unreg
>  );
>  
> -TRACE_EVENT_FN(mmap_lock_released,
> -
> -	TP_PROTO(struct mm_struct *mm, const char *memcg_path, bool write),
> -
> -	TP_ARGS(mm, memcg_path, write),
> -
> -	TP_STRUCT__entry(
> -		__field(struct mm_struct *, mm)
> -		__string(memcg_path, memcg_path)
> -		__field(bool, write)
> -	),
> -
> -	TP_fast_assign(
> -		__entry->mm = mm;
> -		__assign_str(memcg_path, memcg_path);
> -		__entry->write = write;
> -	),
> -
> -	TP_printk(
> -		"mm=%p memcg_path=%s write=%s",
> -		__entry->mm,
> -		__get_str(memcg_path),
> -		__entry->write ? "true" : "false"
> -	),
> -
> -	trace_mmap_lock_reg, trace_mmap_lock_unreg
> -);
> -
>  #endif /* _TRACE_MMAP_LOCK_H */
>  
>  /* This part must be outside protection */
>