Messages in this thread | | | From | Rasmus Villemoes <> | Subject | [PATCH 00/10] implement DYNAMIC_DEBUG_RELATIVE_POINTERS | Date | Tue, 9 Apr 2019 23:25:07 +0200 |
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Similar to CONFIG_GENERIC_BUG_RELATIVE_POINTERS that replaces (8 byte) const char* members by (4 byte) signed offsets from the bug_entry, this implements the similar thing for struct _ddebug, the descriptors underlying pr_debug() and friends in a CONFIG_DYNAMIC_DEBUG kernel.
Since struct _ddebug has four string members, we save 16 byte per instance. The total savings seem to be comparable to what is saved by an architecture selecting GENERIC_BUG_RELATIVE_POINTERS (see patch 8 for some numbers for a common distro config).
While refreshing these patches, which were orignally just targeted at x86-64, it occured to me that despite the implementation relying on inline asm, there's nothing x86 specific about it, and indeed it seems to work out-of-the-box for ppc64 and arm64 as well, but those have only been compile-tested.
The first 6 patches are rather pedestrian preparations. The fun stuff is in patch 7, and the remaining three patches are just the minimal boilerplate to hook up the config option and asm-generic header on the three architectures.
Rasmus Villemoes (10): linux/device.h: use unique identifier for each struct _ddebug linux/net.h: use unique identifier for each struct _ddebug linux/printk.h: use unique identifier for each struct _ddebug dynamic_debug: introduce accessors for string members of struct _ddebug dynamic_debug: drop use of bitfields in struct _ddebug dynamic_debug: introduce CONFIG_DYNAMIC_DEBUG_RELATIVE_POINTERS dynamic_debug: add asm-generic implementation for DYNAMIC_DEBUG_RELATIVE_POINTERS x86-64: select DYNAMIC_DEBUG_RELATIVE_POINTERS arm64: select DYNAMIC_DEBUG_RELATIVE_POINTERS powerpc: select DYNAMIC_DEBUG_RELATIVE_POINTERS for PPC64
arch/arm64/Kconfig | 1 + arch/arm64/include/asm/Kbuild | 1 + arch/powerpc/Kconfig | 1 + arch/powerpc/include/asm/Kbuild | 1 + arch/x86/Kconfig | 1 + arch/x86/entry/vdso/vdso32/vclock_gettime.c | 1 + arch/x86/include/asm/Kbuild | 1 + include/asm-generic/dynamic_debug.h | 116 ++++++++++++++++++++ include/linux/device.h | 4 +- include/linux/dynamic_debug.h | 26 +++-- include/linux/jump_label.h | 2 + include/linux/net.h | 4 +- include/linux/printk.h | 4 +- lib/Kconfig.debug | 3 + lib/dynamic_debug.c | 111 ++++++++++++++----- 15 files changed, 237 insertions(+), 40 deletions(-) create mode 100644 include/asm-generic/dynamic_debug.h
-- 2.20.1
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