From 48ebe1cbbeb51879ba4d22775fee1654d94d1cc6 Mon Sep 17 00:00:00 2001 From: "Lorenzo Stoakes (ARM)" Date: Wed, 23 Sep 2026 18:18:11 +0100 Subject: kbuild: compress the kernel with pigz if available The gzip step of a kernel build is very lengthy, especially for larger builds such as allmodconfig. gzip itself cannot be run in parallel, however an alternative tool exists that can, providing the same feature set as gzip itself - pigz - which works as a drop-in replacement. On a 128-core Threadripper, gzip -9 of a 36 MiB x86-64 vmlinux.bin takes 1.6s, and with pigz it takes 0.09s, so the performance increase is significant. Therefore introduce the KPGZIP build variable which specifies the compressor to use for the kernel image and default it to pigz if available, or KGZIP otherwise (which itself defaults to gzip). Modules, packaging and the embedded kernel configuration (CONFIG_IKCONFIG) continue to use KGZIP which defaults to a single-threaded gzip instance. Module compression is run in parallel by make, so pigz offers no benefit there, packaging sits outside the build and the embedded configuration is too small to matter. pigz is executed using scripts/jobserver-exec, which reserves the job slots make has free - necessary, as otherwise pigz would just grab unbounded CPUs. The kernel image compression step is always performed at the end of the build so should typically have all job slots available. pigz always provides byte-for-byte identical output across runs regardless of thread count, but pigz and gzip are not guaranteed to generate the same binary output, so reproducible builds must use the same tools consistently. Also update Documentation/kbuild/kbuild.rst to describe KPGZIP and Documentation/process/changes.rst to list the optional pigz dependency. While there, add entries for the other compressor programs. Finally, update scripts/ver_linux to include the pigz version there. Every x86 build ends with the compression of vmlinux.bin, 36MB for defconfig and over 200MB for allmodconfig, no-op builds are unchanged. Whole build, 128-thread Threadripper 9980X, best of N runs: before after delta ------------------------------- x86 defconfig, touch mm/vma.c, gcc 7.7s 6.0s -1.7s (-22%) x86 defconfig, touch mm/vma.c, clang 6.9s 5.4s -1.5s (-21%) x86 defconfig, clean, gcc 28.2s 26.3s -1.8s (-6%) x86 defconfig, clean, clang 28.7s 27.2s -1.5s (-5%) x86 allmodconfig, touch mm/vma.c, gcc 23.7s 15.4s -8.3s (-35%) x86 allmodconfig, touch mm/vma.c, clang 22.5s 15.6s -7.0s (-31%) x86 allmodconfig, clean, gcc 294.1s 278.6s -15.5s (-5%) x86 allmodconfig, clean, clang 283.9s 266.8s -17.1s (-6%) Suggested-by: Kees Cook Link: https://zlib.net/pigz/ Assisted-by: LLM Reviewed-by: Manuel Ebner Reviewed-by: Kees Cook Signed-off-by: Lorenzo Stoakes (ARM) Link: https://patch.msgid.link/20260923-build-speedup-v4-22-73128809a4a4@kernel.org Signed-off-by: Nathan Chancellor --- scripts/Makefile.lib | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'scripts/Makefile.lib') diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 0a4fdd8bd975..19e96b30a122 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -333,11 +333,11 @@ quiet_cmd_ar = AR $@ quiet_cmd_objcopy = OBJCOPY $@ cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@ -# Gzip +# Gzip, for the kernel image # --------------------------------------------------------------------------- quiet_cmd_gzip = GZIP $@ - cmd_gzip = cat $(real-prereqs) | $(KGZIP) -n -f -9 > $@ + cmd_gzip = cat $(real-prereqs) | $(KPGZIP) -n -f -9 > $@ # Bzip2 # --------------------------------------------------------------------------- -- cgit v1.2.3