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From: Ezequiel Garcia <elezegarcia@gmail.com>
To: <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>
Cc: Ezequiel Garcia <elezegarcia@gmail.com>, Michal Marek <mmarek@suse.cz>
Subject: [PATCH 01/10] Makefile: Add option CONFIG_DISABLE_GCC_AUTOMATIC_INLINING
Date: Sat,  8 Sep 2012 17:47:50 -0300	[thread overview]
Message-ID: <1347137279-17568-1-git-send-email-elezegarcia@gmail.com> (raw)

As its name suggest this option prevents gcc from auto inlining
small functions. This is very important if one wants to obtain
traces with accurate call sites.

Without this option, gcc will collapse some small functions,
even when not marked as 'inline' thus making impossible to
correlate the trace caller address to the real function it belongs.

Of course, the resultant kernel is slower and slightly smaller,
but that's not an issue if the focus is on tracing accuracy.

Cc: Michal Marek <mmarek@suse.cz>
Signed-off-by: Ezequiel Garcia <elezegarcia@gmail.com>
---
 Makefile          |    4 ++++
 lib/Kconfig.debug |   11 +++++++++++
 2 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/Makefile b/Makefile
index ddf5be9..df6045a 100644
--- a/Makefile
+++ b/Makefile
@@ -561,6 +561,10 @@ else
 KBUILD_CFLAGS	+= -O2
 endif
 
+ifdef CONFIG_DISABLE_GCC_AUTOMATIC_INLINING
+KBUILD_CFLAGS	+= -fno-inline-small-functions
+endif
+
 include $(srctree)/arch/$(SRCARCH)/Makefile
 
 ifdef CONFIG_READABLE_ASM
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2403a63..c8fd50f 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1265,6 +1265,17 @@ config LATENCYTOP
 source mm/Kconfig.debug
 source kernel/trace/Kconfig
 
+config DISABLE_GCC_AUTOMATIC_INLINING
+	bool "Disable gcc automatic inlining"
+	depends on TRACING
+	help
+	  This option tells gcc he's not allowed to inline functions automatically,
+	  when they are not marked as 'inline'.
+	  In turn, this enables to trace an event with an accurate call site.
+	  Of course, the resultant kernel is slower and slightly smaller.
+
+	  Select this option only if you want to trace call sites accurately.
+
 config PROVIDE_OHCI1394_DMA_INIT
 	bool "Remote debugging over FireWire early on boot"
 	depends on PCI && X86
-- 
1.7.8.6


WARNING: multiple messages have this Message-ID (diff)
From: Ezequiel Garcia <elezegarcia@gmail.com>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: Ezequiel Garcia <elezegarcia@gmail.com>, Michal Marek <mmarek@suse.cz>
Subject: [PATCH 01/10] Makefile: Add option CONFIG_DISABLE_GCC_AUTOMATIC_INLINING
Date: Sat,  8 Sep 2012 17:47:50 -0300	[thread overview]
Message-ID: <1347137279-17568-1-git-send-email-elezegarcia@gmail.com> (raw)

As its name suggest this option prevents gcc from auto inlining
small functions. This is very important if one wants to obtain
traces with accurate call sites.

Without this option, gcc will collapse some small functions,
even when not marked as 'inline' thus making impossible to
correlate the trace caller address to the real function it belongs.

Of course, the resultant kernel is slower and slightly smaller,
but that's not an issue if the focus is on tracing accuracy.

Cc: Michal Marek <mmarek@suse.cz>
Signed-off-by: Ezequiel Garcia <elezegarcia@gmail.com>
---
 Makefile          |    4 ++++
 lib/Kconfig.debug |   11 +++++++++++
 2 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/Makefile b/Makefile
index ddf5be9..df6045a 100644
--- a/Makefile
+++ b/Makefile
@@ -561,6 +561,10 @@ else
 KBUILD_CFLAGS	+= -O2
 endif
 
+ifdef CONFIG_DISABLE_GCC_AUTOMATIC_INLINING
+KBUILD_CFLAGS	+= -fno-inline-small-functions
+endif
+
 include $(srctree)/arch/$(SRCARCH)/Makefile
 
 ifdef CONFIG_READABLE_ASM
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2403a63..c8fd50f 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1265,6 +1265,17 @@ config LATENCYTOP
 source mm/Kconfig.debug
 source kernel/trace/Kconfig
 
+config DISABLE_GCC_AUTOMATIC_INLINING
+	bool "Disable gcc automatic inlining"
+	depends on TRACING
+	help
+	  This option tells gcc he's not allowed to inline functions automatically,
+	  when they are not marked as 'inline'.
+	  In turn, this enables to trace an event with an accurate call site.
+	  Of course, the resultant kernel is slower and slightly smaller.
+
+	  Select this option only if you want to trace call sites accurately.
+
 config PROVIDE_OHCI1394_DMA_INIT
 	bool "Remote debugging over FireWire early on boot"
 	depends on PCI && X86
-- 
1.7.8.6

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             reply	other threads:[~2012-09-08 20:56 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-09-08 20:47 Ezequiel Garcia [this message]
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
2012-09-08 20:47   ` Ezequiel Garcia
2012-09-09 21:27   ` David Rientjes
2012-09-09 21:27     ` David Rientjes
2012-09-24 17:13     ` Ezequiel Garcia
2012-09-24 17:13       ` Ezequiel Garcia
2012-09-25  7:37       ` Pekka Enberg
2012-09-25  7:37         ` Pekka Enberg
2012-09-25 10:13         ` Ezequiel Garcia
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
2012-09-08 20:47   ` Ezequiel Garcia
2012-09-09 21:28   ` David Rientjes
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
2012-09-08 20:47   ` 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 19:53     ` David Rientjes
2012-09-25 19:55     ` Ezequiel Garcia
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
2012-09-08 20:47   ` Ezequiel Garcia
2012-09-25  7:15   ` Pekka Enberg
2012-09-25  7:15     ` Pekka Enberg
2012-09-25 21:29   ` Andrew Morton
2012-09-25 21:29     ` Andrew Morton
2012-09-26  1:15     ` Ezequiel Garcia
2012-09-26  1:15       ` Ezequiel Garcia
2012-09-26 21:42       ` Andrew Morton
2012-09-26 21:42         ` Andrew Morton
2012-09-26 21:51         ` Ezequiel Garcia
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   ` 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   ` Ezequiel Garcia
2012-09-08 20:47 ` [PATCH 08/10] mm, slab: Rename __cache_alloc() -> slab_alloc() Ezequiel Garcia
2012-09-08 20:47   ` 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   ` Ezequiel Garcia
2012-09-08 20:47 ` [PATCH 10/10] mm: Factor SLAB and SLUB common code Ezequiel Garcia
2012-09-08 20:47   ` Ezequiel Garcia
2012-09-08 21:43 ` [PATCH 01/10] Makefile: Add option CONFIG_DISABLE_GCC_AUTOMATIC_INLINING Sam Ravnborg
2012-09-08 21:43   ` Sam Ravnborg
2012-09-09 21:25 ` David Rientjes
2012-09-09 21:25   ` David Rientjes
2012-09-13  0:30   ` Ezequiel Garcia
2012-09-13  0:30     ` Ezequiel Garcia
2012-09-13  7:17     ` Michal Marek
2012-09-13  7:17       ` Michal Marek
2012-09-13  9:16       ` Ezequiel Garcia
2012-09-13  9:16         ` Ezequiel Garcia

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