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authorHeiko Carstens <heiko.carstens@de.ibm.com>2015-01-09 13:08:28 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2015-01-29 09:19:25 +0100
commite6d60b368b45b9be3aa068f8e5fa98c3487c9d4e (patch)
treeabe83543f72b5cd5d5de309dab8551f93c34f023 /arch/s390/Makefile
parent61f552141c9c0e88b3fdc7046265781ffd8fa68a (diff)
downloadlinux-e6d60b368b45b9be3aa068f8e5fa98c3487c9d4e.tar.bz2
s390/ftrace: hotpatch support for function tracing
Make use of gcc's hotpatch support to generate better code for ftrace function tracing. The generated code now contains only a six byte nop in each function prologue instead of a 24 byte code block which will be runtime patched to support function tracing. With the new code generation the runtime overhead for supporting function tracing is close to zero, while the original code did show a significant performance impact. Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/Makefile')
-rw-r--r--arch/s390/Makefile10
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/s390/Makefile b/arch/s390/Makefile
index e742ec5de9a7..acb6859c6a95 100644
--- a/arch/s390/Makefile
+++ b/arch/s390/Makefile
@@ -87,6 +87,16 @@ ifeq ($(call cc-option-yn,-mwarn-dynamicstack),y)
cflags-$(CONFIG_WARN_DYNAMIC_STACK) += -mwarn-dynamicstack
endif
+ifdef CONFIG_FUNCTION_TRACER
+# make use of hotpatch feature if the compiler supports it
+cc_hotpatch := -mhotpatch=0,3
+ifeq ($(call cc-option-yn,$(cc_hotpatch)),y)
+CC_FLAGS_FTRACE := $(cc_hotpatch)
+KBUILD_AFLAGS += -DCC_USING_HOTPATCH
+KBUILD_CFLAGS += -DCC_USING_HOTPATCH
+endif
+endif
+
KBUILD_CFLAGS += -mbackchain -msoft-float $(cflags-y)
KBUILD_CFLAGS += -pipe -fno-strength-reduce -Wno-sign-compare
KBUILD_AFLAGS += $(aflags-y)