Re: [RFC v2 2/3] mm: introduce show_page_types() to provide human-readable page_type

[Steven Rostedt <rostedt@goodmis.org>]

On Sun,  6 Nov 2022 23:03:54 +0900
Hyeonggon Yoo <42.hyeyoo@gmail.com> wrote:

> Some page flags are not actually set in 'flags' field. To provide
> better understanding of tracepoint output, introduce show_page_types()
> that shows page flags from page_type.
> 
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Andrey Konovalov <andreyknvl@gmail.com>
> Cc: Marco Elver <elver@google.com>
> Cc: Vasily Averin <vasily.averin@linux.dev>
> Cc: NeilBrown <neilb@suse.de>
> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> ---
>  include/trace/events/mmflags.h  | 12 ++++++++++++
>  include/trace/events/page_ref.h | 10 ++++++++--
>  2 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
> index 72c11a16f771..a8dfb98a4dd6 100644
> --- a/include/trace/events/mmflags.h
> +++ b/include/trace/events/mmflags.h
> @@ -136,6 +136,18 @@ IF_HAVE_PG_SKIP_KASAN_POISON(PG_skip_kasan_poison, "skip_kasan_poison")
>  	__def_pageflag_names						\
>  	) : "none"
>  
> +#define __def_pagetype_names						\
> +	{PG_slab,			"slab"		},		\
> +	{PG_offline,			"offline"	},		\
> +	{PG_guard,			"guard"		},		\
> +	{PG_table,			"table"		},		\
> +	{PG_buddy,			"buddy"		}
> +
> +#define show_page_types(page_type)					\
> +	page_type_has_type(page_type) ?					\
> +		__print_flags((~page_type), "|", __def_pagetype_names)	\
> +	: "none"
> +
>  #if defined(CONFIG_X86)
>  #define __VM_ARCH_SPECIFIC_1 {VM_PAT,     "pat"           }
>  #elif defined(CONFIG_PPC)
> diff --git a/include/trace/events/page_ref.h b/include/trace/events/page_ref.h
> index 8a99c1cd417b..b00d23e90e93 100644
> --- a/include/trace/events/page_ref.h
> +++ b/include/trace/events/page_ref.h
> @@ -21,6 +21,7 @@ DECLARE_EVENT_CLASS(page_ref_mod_template,
>  		__field(unsigned long, flags)
>  		__field(int, count)
>  		__field(int, mapcount)
> +		__field(unsigned int, page_type)

Be careful were you add int fields for 64 bit machines.

The above is going to add 4 bytes of nothing in the ring buffer for
each event. Please try to keep ints together by 2s, especially between
long and pointer fields.

>  		__field(void *, mapping)
>  		__field(int, mt)
>  		__field(int, val)
> @@ -31,14 +32,16 @@ DECLARE_EVENT_CLASS(page_ref_mod_template,
>  		__entry->flags = page->flags;
>  		__entry->count = page_ref_count(page);
>  		__entry->mapcount = page_mapcount(page);
> +		__entry->page_type = page->page_type;
>  		__entry->mapping = page->mapping;
>  		__entry->mt = get_pageblock_migratetype(page);
>  		__entry->val = v;
>  	),
>  
> -	TP_printk("pfn=0x%lx flags=%s count=%d mapcount=%d mapping=%p mt=%d val=%d",
> +	TP_printk("pfn=0x%lx flags=%s page_type=%s count=%d mapcount=%d mapping=%p mt=%d val=%d",
>  		__entry->pfn,
>  		show_page_flags(__entry->flags & PAGEFLAGS_MASK),
> +		show_page_types(__entry->page_type & PAGE_TYPE_MASK),
>  		__entry->count,
>  		__entry->mapcount, __entry->mapping, __entry->mt,
>  		__entry->val)
> @@ -69,6 +72,7 @@ DECLARE_EVENT_CLASS(page_ref_mod_and_test_template,
>  		__field(unsigned long, flags)
>  		__field(int, count)
>  		__field(int, mapcount)
> +		__field(unsigned int, page_type)

Here too.

-- Steve

>  		__field(void *, mapping)
>  		__field(int, mt)
>  		__field(int, val)
> @@ -80,15 +84,17 @@ DECLARE_EVENT_CLASS(page_ref_mod_and_test_template,
>  		__entry->flags = page->flags;
>  		__entry->count = page_ref_count(page);
>  		__entry->mapcount = page_mapcount(page);
> +		__entry->page_type = page->page_type;
>  		__entry->mapping = page->mapping;
>  		__entry->mt = get_pageblock_migratetype(page);
>  		__entry->val = v;
>  		__entry->ret = ret;
>  	),
>  
> -	TP_printk("pfn=0x%lx flags=%s count=%d mapcount=%d mapping=%p mt=%d val=%d ret=%d",
> +	TP_printk("pfn=0x%lx flags=%s page_type=%s count=%d mapcount=%d mapping=%p mt=%d val=%d ret=%d",
>  		__entry->pfn,
>  		show_page_flags(__entry->flags & PAGEFLAGS_MASK),
> +		show_page_types(__entry->page_type & PAGE_TYPE_MASK),
>  		__entry->count,
>  		__entry->mapcount, __entry->mapping, __entry->mt,
>  		__entry->val, __entry->ret)