From: Vlastimil Babka <vbabka@suse.cz>
To: js1304@gmail.com, Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Nazarewicz <mina86@mina86.com>,
Minchan Kim <minchan@kernel.org>,
Mel Gorman <mgorman@techsingularity.net>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-api@vger.kernel.org, Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH v4 2/2] mm/page_ref: add tracepoint to track down page reference manipulation
Date: Wed, 2 Mar 2016 17:58:26 +0100 [thread overview]
Message-ID: <56D71BB2.5060503@suse.cz> (raw)
In-Reply-To: <1456448282-897-2-git-send-email-iamjoonsoo.kim@lge.com>
On 02/26/2016 01:58 AM, js1304@gmail.com wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>
> CMA allocation should be guaranteed to succeed by definition, but,
> unfortunately, it would be failed sometimes. It is hard to track down
> the problem, because it is related to page reference manipulation and
> we don't have any facility to analyze it.
>
> This patch adds tracepoints to track down page reference manipulation.
> With it, we can find exact reason of failure and can fix the problem.
> Following is an example of tracepoint output. (note: this example is
> stale version that printing flags as the number. Recent version will
> print it as human readable string.)
>
> Enabling this feature bloat kernel text 30 KB in my configuration.
>
> text data bss dec hex filename
> 12127327 2243616 1507328 15878271 f2487f vmlinux_disabled
> 12157208 2258880 1507328 15923416 f2f8d8 vmlinux_enabled
>
That's not bad, and it's even configurable. Thanks for taking the extra
care about overhead since v1.
> Note that, due to header file dependency problem between mm.h and
> tracepoint.h, this feature has to open code the static key functions
> for tracepoints. Proposed by Steven Rostedt in following link.
>
> https://lkml.org/lkml/2015/12/9/699
>
> v3:
> o Add commit description and code comment why this patch open code
> the static key functions for tracepoints.
> o Notify that example is stale version.
> o Add "depends on TRACEPOINTS".
>
> v2:
> o Use static key of each tracepoints to avoid function call overhead
> when tracepoints are disabled.
> o Print human-readable page flag thanks to newly introduced %pgp option.
> o Add more description to Kconfig.debug.
>
> Acked-by: Michal Nazarewicz <mina86@mina86.com>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
> +config DEBUG_PAGE_REF
> + bool "Enable tracepoint to track down page reference manipulation"
> + depends on DEBUG_KERNEL
> + depends on TRACEPOINTS
> + ---help---
> + This is the feature to add tracepoint for tracking down page reference
> + manipulation. This tracking is useful to diagnosis functional failure
> + due to migration failure caused by page reference mismatch. Be
OK.
> + careful to turn on this feature because it could bloat some kernel
> + text. In my configuration, it bloats 30 KB. Although kernel text will
> + be bloated, there would be no runtime performance overhead if
> + tracepoint isn't enabled thanks to jump label.
I would just write something like:
Enabling this feature adds about 30 KB to the kernel code, but runtime
performance overhead is virtually none until the tracepoints are
actually enabled.
next prev parent reply other threads:[~2016-03-02 16:58 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-26 0:58 [PATCH v4 1/2] mm: introduce page reference manipulation functions js1304
2016-02-26 0:58 ` [PATCH v4 2/2] mm/page_ref: add tracepoint to track down page reference manipulation js1304
2016-02-26 16:38 ` Steven Rostedt
2016-03-02 16:58 ` Vlastimil Babka [this message]
2016-03-03 7:43 ` Joonsoo Kim
2016-03-04 20:04 ` Andrew Morton
2016-03-07 4:20 ` Joonsoo Kim
2016-03-02 16:44 ` [PATCH v4 1/2] mm: introduce page reference manipulation functions Vlastimil Babka
2016-03-03 7:47 ` Joonsoo Kim
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