From: Ezequiel Garcia <elezegarcia@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Pekka Enberg <penberg@kernel.org>
Subject: Re: [PATCH 05/10] mm, util: Use dup_user to duplicate user memory
Date: Tue, 25 Sep 2012 22:15:38 -0300 [thread overview]
Message-ID: <CALF0-+WcXLR_akn8mL8u-QigHU9Bk5RotA3tbodZ8rhZsxpFLg@mail.gmail.com> (raw)
In-Reply-To: <20120925142948.6b062cb6.akpm@linux-foundation.org>
Hi Andrew,
On Tue, Sep 25, 2012 at 6:29 PM, Andrew Morton
<akpm@linux-foundation.org> wrote:
> On Sat, 8 Sep 2012 17:47:54 -0300
> Ezequiel Garcia <elezegarcia@gmail.com> wrote:
>
>> Previously the strndup_user allocation was being done through memdup_user,
>> and the caller was wrongly traced as being strndup_user
>> (the correct trace must report the caller of strndup_user).
>>
>> This is a common problem: in order to get accurate callsite tracing,
>> a utils function can't allocate through another utils function,
>> but instead do the allocation himself (or inlined).
>>
>> Here we fix this by creating an always inlined dup_user() function to
>> performed the real allocation and to be used by memdup_user and strndup_user.
>
> This patch increases util.o's text size by 238 bytes. A larger kernel
> with a worsened cache footprint.
>
> And we did this to get marginally improved tracing output? This sounds
> like a bad tradeoff to me.
>
Mmm, that's bad tradeoff indeed.
It's certainly odd since the patch shouldn't increase the text size
*that* much.
Is it too much to ask that you send your kernel config and gcc version.
My compilation (x86 kernel in gcc 4.7.1) shows a kernel less bloated:
$ readelf -s util-dup-user.o | grep dup_user
161: 00001c10 108 FUNC GLOBAL DEFAULT 1 memdup_user
169: 00001df0 159 FUNC GLOBAL DEFAULT 1 strndup_user
$ readelf -s util.o | grep dup_user
161: 00001c10 108 FUNC GLOBAL DEFAULT 1 memdup_user
169: 00001df0 98 FUNC GLOBAL DEFAULT 1 strndup_user
$ size util.o
text data bss dec hex filename
18319 2077 0 20396 4fac util.o
$ size util-dup-user.o
text data bss dec hex filename
18367 2077 0 20444 4fdc util-dup-user.o
Am I doing anything wrong?
If you still feel this is unnecessary bloatness, perhaps I could think of
something depending on CONFIG_TRACING (though I know
we all hate those nasty ifdefs).
Anyway, thanks for the review,
Ezequiel.
next prev parent reply other threads:[~2012-09-26 1:15 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-08 20:47 [PATCH 01/10] Makefile: Add option CONFIG_DISABLE_GCC_AUTOMATIC_INLINING Ezequiel Garcia
2012-09-08 20:47 ` [PATCH 02/10] mm, slob: Use NUMA_NO_NODE instead of -1 Ezequiel Garcia
2012-09-09 21:27 ` David Rientjes
2012-09-24 17:13 ` Ezequiel Garcia
2012-09-25 7:37 ` Pekka Enberg
2012-09-25 10:13 ` Ezequiel Garcia
2012-09-08 20:47 ` [PATCH 03/10] mm, slab: Remove silly function slab_buffer_size() Ezequiel Garcia
2012-09-09 21:28 ` David Rientjes
2012-09-08 20:47 ` [PATCH 04/10] mm, slob: Add support for kmalloc_track_caller() Ezequiel Garcia
2012-09-25 19:53 ` [patch slab/next] mm, slob: fix build breakage in __kmalloc_node_track_caller David Rientjes
2012-09-25 19:55 ` Ezequiel Garcia
2012-09-08 20:47 ` [PATCH 05/10] mm, util: Use dup_user to duplicate user memory Ezequiel Garcia
2012-09-25 7:15 ` Pekka Enberg
2012-09-25 21:29 ` Andrew Morton
2012-09-26 1:15 ` Ezequiel Garcia [this message]
2012-09-26 21:42 ` Andrew Morton
2012-09-26 21:51 ` Ezequiel Garcia
2012-09-08 20:47 ` [PATCH 06/10] mm, slab: Replace 'caller' type, void* -> unsigned long Ezequiel Garcia
2012-09-08 20:47 ` [PATCH 07/10] mm, slab: Match SLAB and SLUB kmem_cache_alloc_xxx_trace() prototype Ezequiel Garcia
2012-09-08 20:47 ` [PATCH 08/10] mm, slab: Rename __cache_alloc() -> slab_alloc() Ezequiel Garcia
2012-09-08 20:47 ` [PATCH 09/10] mm, slub: Rename slab_alloc() -> slab_alloc_node() to match SLAB Ezequiel Garcia
2012-09-08 20:47 ` [PATCH 10/10] mm: Factor SLAB and SLUB common code Ezequiel Garcia
2012-09-08 21:43 ` [PATCH 01/10] Makefile: Add option CONFIG_DISABLE_GCC_AUTOMATIC_INLINING Sam Ravnborg
2012-09-09 21:25 ` David Rientjes
2012-09-13 0:30 ` Ezequiel Garcia
2012-09-13 7:17 ` Michal Marek
2012-09-13 9:16 ` Ezequiel Garcia
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