https://bugzilla.suse.com/show_bug.cgi?id=1177403 Bug ID: 1177403 Summary: Impact of DEBUG_SECTION_MISMATCH Classification: openSUSE Product: openSUSE Tumbleweed Version: Current Hardware: Other OS: Other Status: NEW Severity: Normal Priority: P5 - None Component: Kernel Assignee: kernel-performance-bugs@suse.de Reporter: jslaby@suse.com QA Contact: qa-bugs@suse.de CC: jslaby@suse.com, lpechacek@suse.com, mbenes@suse.com, nstange@suse.com, petr.vorel@suse.com, pmladek@suse.com Found By: --- Blocker: --- +++ This bug was initially created as a clone of Bug #1176907 +++ We enable DEBUG_SECTION_MISMATCH in our kernels to find potential problems with section mismatches: $ git grep CONFIG_DEBUG_SECTION_MISMATCH `git branch -rl 'origin/[So][Lp][Ee]*[0-9]' 'origin/[ms][at][sa]*'` -- config/x86_64/default|sort origin/master:config/x86_64/default:CONFIG_DEBUG_SECTION_MISMATCH=y origin/openSUSE-15.1:config/x86_64/default:CONFIG_DEBUG_SECTION_MISMATCH=y origin/openSUSE-15.2:config/x86_64/default:CONFIG_DEBUG_SECTION_MISMATCH=y origin/SLE12-SP4:config/x86_64/default:CONFIG_DEBUG_SECTION_MISMATCH=y origin/SLE12-SP5:config/x86_64/default:CONFIG_DEBUG_SECTION_MISMATCH=y origin/SLE15-SP1:config/x86_64/default:CONFIG_DEBUG_SECTION_MISMATCH=y origin/SLE15-SP2:config/x86_64/default:CONFIG_DEBUG_SECTION_MISMATCH=y origin/SLE15-SP3:config/x86_64/default:CONFIG_DEBUG_SECTION_MISMATCH=y origin/stable:config/x86_64/default:CONFIG_DEBUG_SECTION_MISMATCH=y It turned out that DEBUG_SECTION_MISMATCH disables inlining of some functions by -fno-inline-functions-called-once. Makefile says: # We trigger additional mismatches with less inlining ifdef CONFIG_DEBUG_SECTION_MISMATCH KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once) endif There are only few defconfigs to enable the option in the (upstream) tree: $ git grep DEBUG_SECTION_MISMATCH arch/ arch/arc/configs/tb10x_defconfig:CONFIG_DEBUG_SECTION_MISMATCH=y arch/arm/configs/prima2_defconfig:CONFIG_DEBUG_SECTION_MISMATCH=y arch/nds32/configs/defconfig:CONFIG_DEBUG_SECTION_MISMATCH=y arch/s390/configs/debug_defconfig:CONFIG_DEBUG_SECTION_MISMATCH=y arch/s390/configs/defconfig:CONFIG_DEBUG_SECTION_MISMATCH=y defconfig vmlinux is by 2M larger with DEBUG_SECTION_MISMATCH=y: -rwxr-xr-x 1 jslaby users 57M Oct 7 08:10 ../def-dis/vmlinux -rwxr-xr-x 1 jslaby users 59M Oct 7 08:10 ../def-en/vmlinux The question is what's the performance impact of the option? Performance team, could you do some quick measurements? Thanks. -- You are receiving this mail because: You are on the CC list for the bug.