cc62242079
Enabling gcov is counterproductive to compile testing: it significantly increases the kernel image size, compile time, and it produces lots of false positive "may be used uninitialized" warnings as the result of missed optimizations. This is in line with how UBSAN_SANITIZE_ALL and PROFILE_ALL_BRANCHES work, both of which have similar problems. With an ARM allmodconfig kernel, I see the build time drop from 283 minutes CPU time to 225 minutes, and the vmlinux size drops from 43MB to 26MB. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com> Signed-off-by: Michal Marek <mmarek@suse.com>
2.1 KiB
menu "GCOV-based kernel profiling"
config GCOV_KERNEL bool "Enable gcov-based kernel profiling" depends on DEBUG_FS select CONSTRUCTORS if !UML default n ---help--- This option enables gcov-based code profiling (e.g. for code coverage measurements).
If unsure, say N.
Additionally specify CONFIG_GCOV_PROFILE_ALL=y to get profiling data
for the entire kernel. To enable profiling for specific files or
directories, add a line similar to the following to the respective
Makefile:
For a single file (e.g. main.o):
GCOV_PROFILE_main.o := y
For all files in one directory:
GCOV_PROFILE := y
To exclude files from being profiled even when CONFIG_GCOV_PROFILE_ALL
is specified, use:
GCOV_PROFILE_main.o := n
and:
GCOV_PROFILE := n
Note that the debugfs filesystem has to be mounted to access
profiling data.
config ARCH_HAS_GCOV_PROFILE_ALL def_bool n
config GCOV_PROFILE_ALL bool "Profile entire Kernel" depends on !COMPILE_TEST depends on GCOV_KERNEL depends on ARCH_HAS_GCOV_PROFILE_ALL default n ---help--- This options activates profiling for the entire kernel.
If unsure, say N.
Note that a kernel compiled with profiling flags will be significantly
larger and run slower. Also be sure to exclude files from profiling
which are not linked to the kernel image to prevent linker errors.
choice prompt "Specify GCOV format" depends on GCOV_KERNEL default GCOV_FORMAT_AUTODETECT ---help--- The gcov format is usually determined by the GCC version, but there are exceptions where format changes are integrated in lower-version GCCs. In such a case use this option to adjust the format used in the kernel accordingly.
If unsure, choose "Autodetect".
config GCOV_FORMAT_AUTODETECT bool "Autodetect" ---help--- Select this option to use the format that corresponds to your GCC version.
config GCOV_FORMAT_3_4 bool "GCC 3.4 format" ---help--- Select this option to use the format defined by GCC 3.4.
config GCOV_FORMAT_4_7 bool "GCC 4.7 format" ---help--- Select this option to use the format defined by GCC 4.7.
endchoice
endmenu