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| Started by | Arnd Bergmann <arnd@arndb.de> |
|---|---|
| First post | 2016-02-12 17:10 +0100 |
| Last post | 2016-02-15 15:30 +0100 |
| Articles | 2 — 2 participants |
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[PATCH 3/5] gcov: disable for COMPILE_TEST Arnd Bergmann <arnd@arndb.de> - 2016-02-12 17:10 +0100
Re: [PATCH 3/5] gcov: disable for COMPILE_TEST Peter Oberparleiter <oberpar@linux.vnet.ibm.com> - 2016-02-15 15:30 +0100
| From | Arnd Bergmann <arnd@arndb.de> |
|---|---|
| Date | 2016-02-12 17:10 +0100 |
| Subject | [PATCH 3/5] gcov: disable for COMPILE_TEST |
| Message-ID | <r1os9-Pl-3@gated-at.bofh.it> |
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> --- kernel/gcov/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/gcov/Kconfig b/kernel/gcov/Kconfig index c92e44855ddd..1276aabaab55 100644 --- a/kernel/gcov/Kconfig +++ b/kernel/gcov/Kconfig @@ -37,6 +37,7 @@ config ARCH_HAS_GCOV_PROFILE_ALL 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 -- 2.7.0
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| From | Peter Oberparleiter <oberpar@linux.vnet.ibm.com> |
|---|---|
| Date | 2016-02-15 15:30 +0100 |
| Message-ID | <r2sk2-2aV-15@gated-at.bofh.it> |
| In reply to | #1332837 |
On 12.02.2016 17:06, Arnd Bergmann wrote: > 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> Agreed that COMPILE_TEST + GCOV_PROFILE_ALL is a very exotic combination with little added use. Acked-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com> > --- > kernel/gcov/Kconfig | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/gcov/Kconfig b/kernel/gcov/Kconfig > index c92e44855ddd..1276aabaab55 100644 > --- a/kernel/gcov/Kconfig > +++ b/kernel/gcov/Kconfig > @@ -37,6 +37,7 @@ config ARCH_HAS_GCOV_PROFILE_ALL > > 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 > -- Peter Oberparleiter Linux on z Systems Development - IBM Germany
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