2020-05-25 17:44:07

by Cixi Geng

Subject: [RFC PATCH v4] GCOV: profile by modules

From: Cixi Geng <[email protected]>

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.

Only add SERIAL_GCOV for an example.

Signed-off-by: Cixi Geng <[email protected]>
---
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.o
diff --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.
+
choice
prompt "Specify GCOV format"
depends on GCOV_KERNEL
--
2.17.1

2020-05-28 14:50:40

by Peter Oberparleiter

Subject: Re: [RFC PATCH v4] GCOV: profile by modules

On 25.05.2020 12:00, [email protected] wrote:
> From: Cixi Geng <[email protected]>
>
> 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.

>
> Only add SERIAL_GCOV for an example.
>
> Signed-off-by: Cixi Geng <[email protected]>
> ---
> 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.o
> diff --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

2020-06-01 11:01:01

by Cixi Geng

Subject: Re: [RFC PATCH v4] GCOV: profile by modules

Peter Oberparleiter <[email protected]> 于2020年5月28日周四 下午10:47写道：
>
> On 25.05.2020 12:00, [email protected] wrote:
> > From: Cixi Geng <[email protected]>
> >
> > 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.
>
> >
> > Only add SERIAL_GCOV for an example.
> >
> > Signed-off-by: Cixi Geng <[email protected]>
> > ---
> > 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.o
> > diff --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).
>
As far as I'm concerned, The GCOV_KERNEL_ALL will conflict with
GCOV_PROFILE_PREREQS，since the GCOV_KERNEL_ALL will profing all
code which contain the new config.
>
> > +
> > choice
> > prompt "Specify GCOV format"
> > depends on GCOV_KERNEL
> >
>
>
> --
> Peter Oberparleiter
> Linux on Z Development - IBM Germany