linux-kernel - Re: [RFC][PATCH V3] GCOV: profile by modules

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Date:   Fri, 22 May 2020 18:46:34 +0800
From:   Cixi Geng <gengcixi@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     jslaby@...e.com, oberpar@...ux.ibm.com,
        linux-serial@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Orson Zhai <orsonzhai@...il.com>, zhang.lyra@...il.com,
        Cixi Geng <cixi.geng1@...soc.com>
Subject: Re: [RFC][PATCH V3] GCOV: profile by modules

Hi Greg:
DId you mean that the GCOV_PROFILE_PREREQS should add depends
on !GCOV_PROFILE_ALL ,then when GCOV_PROFILE_ALL is enabled,
the config GCOV_PROFILE_PREREQS will no longer works.

Greg KH <gregkh@...uxfoundation.org> 于2020年5月22日周五 下午4:37写道：
>
> On Fri, May 22, 2020 at 03:19:17PM +0800, gengcixi@...il.com wrote:
> > From: Cixi Geng <cixi.geng1@...soc.com>
> >
> > 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 <cixi.geng1@...soc.com>
> > ---
> >  drivers/tty/serial/Kconfig  |  7 +++++++
> >  drivers/tty/serial/Makefile |  1 +
> >  kernel/gcov/Kconfig         | 13 +++++++++++++
> >  3 files changed, 21 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..4d75fa158726 100644
> > --- a/kernel/gcov/Kconfig
> > +++ b/kernel/gcov/Kconfig
> > @@ -51,6 +51,19 @@ 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
> > +     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
>
>
> I understand the goal here, but don't you need to have the main GCov
> option depend on your new Kconfig option here?  You have it switched
> around here, so what keeps all code from being built with gcov support
> at the moment?
>
> thanks,
>
> greg k-h