On Thu, Sep 17, 2026 at 05:06:14PM +0100, Lorenzo Stoakes (ARM) wrote: > Unless instructed otherwise, nm sorts by name. > > There are places where this is unnecessary - an invocation from > scripts/sorttable every vmlinux link, scripts/check-function-names.sh run > after every vmlinux.o link, and the x86 VOFFSET and ZOFFSET listings > between vmlinux and bzImage. > > Both GNU nm and llvm-nm accept the same '-p' parameter to disable sorting > in these instances, so use that to prevent this unnecessary work. > > Each nm run on its own, x86-64, median of 5: > > GNU nm 2.47 llvm-nm 22 > before after delta before after delta > defconfig > sorttable, nm -S vmlinux 0.080s 0.039s -0.041s 0.265s 0.113s -0.152s > check-function-names.sh 0.072s 0.033s -0.039s 0.244s 0.102s -0.142s > VOFFSET 0.077s 0.034s -0.043s 0.261s 0.113s -0.148s > ZOFFSET 0.007s 0.005s -0.002s 0.005s 0.005s 0.000s > TOTAL -0.125s -0.442s > > allmodconfig > sorttable, nm -S vmlinux 0.156s 0.063s -0.093s 0.539s 0.223s -0.316s > check-function-names.sh 0.149s 0.054s -0.095s 0.537s 0.217s -0.320s > VOFFSET 0.146s 0.052s -0.094s 0.524s 0.221s -0.303s > ZOFFSET 0.007s 0.005s -0.002s 0.006s 0.004s -0.002s > TOTAL -0.284s -0.941s > > llvm-nm appears to be a lot slower than GNU nm, so these builds naturally > improve the most. > > The four run one after another in the serial tail of every build that links > vmlinux so impact kernel builds directly. > > In an allmodconfig the decompressor is built in parallel while the modules, > so only the two before the vmlinux link contribute to build time. > > The build outputs remain unchanged. > > Whole build, 128-thread Threadripper 9980X, best of N runs: > > before after delta > --------------------------------- > x86 defconfig, touch mm/vma.c, gcc 9.7s 9.5s -0.18s (-2%) > x86 defconfig, touch mm/vma.c, clang 9.3s 9.0s -0.27s (-3%) > x86 defconfig, clean, gcc 30.3s 30.1s -0.16s (-1%) > x86 defconfig, clean, clang 31.7s 31.2s -0.55s (-2%) > x86 allmodconfig, touch mm/vma.c, clang 36.4s 35.8s -0.67s (-2%) > > Assisted-by: LLM > Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]> > --- > arch/x86/boot/Makefile | 2 +- > arch/x86/boot/compressed/Makefile | 2 +- > scripts/check-function-names.sh | 3 ++- > scripts/link-vmlinux.sh | 2 +- > 4 files changed, 5 insertions(+), 4 deletions(-) >
Thanks! Reviewed-by: Nicolas Schier <[email protected]> -- Nicolas
