Re: [RFC PATCH v4] GCOV: profile by modules
From: Peter Oberparleiter <oberpar@linux.ibm.com>
Date: 2020-05-28 14:48:18
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On 25.05.2020 12:00, gengcixi@gmail.com wrote:
From: Cixi Geng <redacted> The CONFIG_GCOV_PROFILE_ALL will compile kernel by profiling entire kernel which will lead to kernel run slower.Use GCOV_PROFILE_PREREQS to control part of the kernel modules to open gcov.
Maybe rephrase the commit message to make the intention more obvious: Introduce new configuration option GCOV_PROFILE_PREREQS that can be used to check whether the prerequisites for enabling gcov profiling for specific files and directories are met.
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Only add SERIAL_GCOV for an example. Signed-off-by: Cixi Geng <redacted> --- drivers/tty/serial/Kconfig | 7 +++++++ drivers/tty/serial/Makefile | 1 + kernel/gcov/Kconfig | 14 ++++++++++++++ 3 files changed, 22 insertions(+)diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig index adf9e80e7dc9..6df002370f18 100644 --- a/drivers/tty/serial/Kconfig +++ b/drivers/tty/serial/Kconfig@@ -1566,3 +1566,10 @@ endmenu config SERIAL_MCTRL_GPIO tristate + +config SERIAL_GCOV + bool "Enable profile gcov for serial directory" + depends on GCOV_PROFILE_PREREQS + help + The SERIAL_GCOV will add Gcov profiling flags when kernel compiles. + Say 'Y' here if you want the gcov data for the serial directory,diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile index d056ee6cca33..17272733db95 100644 --- a/drivers/tty/serial/Makefile +++ b/drivers/tty/serial/Makefile@@ -3,6 +3,7 @@ # Makefile for the kernel serial device drivers. # +GCOV_PROFILE := $(CONFIG_SERIAL_GCOV) obj-$(CONFIG_SERIAL_CORE) += serial_core.o obj-$(CONFIG_SERIAL_EARLYCON) += earlycon.odiff --git a/kernel/gcov/Kconfig b/kernel/gcov/Kconfig index 3941a9c48f83..ea8b514f5676 100644 --- a/kernel/gcov/Kconfig +++ b/kernel/gcov/Kconfig@@ -51,6 +51,20 @@ config GCOV_PROFILE_ALL larger and run slower. Also be sure to exclude files from profiling which are not linked to the kernel image to prevent linker errors. +config GCOV_PROFILE_PREREQS + bool "Profile Kernel subsytem" + depends on !COMPILE_TEST + depends on GCOV_KERNEL + depends on !GCOV_PROFILE_ALL + help + This options activates profiling for the specified kernel modules. + + When some modules need Gcov data, enable this config, then configure + with gcov on the corresponding modules,The directories or files of + these modules will be added profiling flags after kernel compile. + + If unsure, say N.
This is not quite what I had in mind. A user still needs to manually
select GCOV_PROFILE, then GCOV_PROFILE_PREREQS, then SERIAL_GCOV.
My though was that you could provide an automatic config option that is
invisible in the configuration dialog, and that is automatically
selected when all prereqs for enabling GCOV in a module directory are met.
Something like the following:
config GCOV_PROFILE_PREREQS
bool
default y if GCOV_KERNEL && !COMPILE_TEST
default n
There's no need to add GCOV_KERNEL_ALL here since that is about a user
choice ("I want all code compiled with profiling") vs. this new symbol
which is about an ability ("all prereqs for enabling profiling in
specific directories are met).
+ choice prompt "Specify GCOV format" depends on GCOV_KERNEL
-- Peter Oberparleiter Linux on Z Development - IBM Germany