Re: [PATCH 2/2] mm/page_ref: add tracepoint to track down page reference manipulation

From: Joonsoo Kim <js1304@gmail.com>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Michal Nazarewicz <mina86@mina86.com>,
	Minchan Kim <minchan@kernel.org>,
	Mel Gorman <mgorman@techsingularity.net>,
	Vlastimil Babka <vbabka@suse.cz>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Linux Memory Management List <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-api@vger.kernel.org, Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH 2/2] mm/page_ref: add tracepoint to track down page reference manipulation
Date: Mon, 15 Feb 2016 23:18:42 +0900	[thread overview]
Message-ID: <CAAmzW4Nwe45dn5iPKmK_t1F6=+d1K4xqHAn+CfTxL6uvsxQhqw@mail.gmail.com> (raw)
In-Reply-To: <20160215052855.GA2010@swordfish>

2016-02-15 14:28 GMT+09:00 Sergey Senozhatsky
<sergey.senozhatsky.work@gmail.com>:
> On (02/15/16 14:08), Sergey Senozhatsky wrote:
>>
>> will this compile with !CONFIG_TRACEPOINTS config?
>>

Yes, even if !CONFIG_TRACEPOINTS, it is compiled well.

> uh.. sorry, was composed in email client. seems the correct way to do it is
>
> +#if defined CONFIG_DEBUG_PAGE_REF && defined CONFIG_TRACEPOINTS
>
>  #include <linux/tracepoint-defs.h>
>
>  #define page_ref_tracepoint_active(t) static_key_false(&(t).key)
>
>  extern struct tracepoint __tracepoint_page_ref_set;
>  ...
>
>  extern void __page_ref_set(struct page *page, int v);
>  ...
>
> #else
>
>  #define page_ref_tracepoint_active(t) false
>
>  static inline void __page_ref_set(struct page *page, int v)
>  {
>  }
>  ...
>
> #endif
>
>
>
> or add a dependency of PAGE_REF on CONFIG_TRACEPOINTS in Kconfig.

Thanks for catching it.
I will add "depends on CONFIG_TRACEPOINTS" to Kconfig because
this feature has no meaning if !CONFIG_TRACEPOINTS.

Thanks.