# git rev-parse -q --verify 4df910620bebb5cfe234af16ac8f6474b60215fd^{commit} 4df910620bebb5cfe234af16ac8f6474b60215fd already have revision, skipping fetch # git checkout -q -f -B kisskb 4df910620bebb5cfe234af16ac8f6474b60215fd # git clean -qxdf # < git log -1 # commit 4df910620bebb5cfe234af16ac8f6474b60215fd # Author: Feng Tang # Date: Wed Nov 25 13:22:21 2020 +0800 # # mm: memcg: relayout structure mem_cgroup to avoid cache interference # # 0day reported one -22.7% regression for will-it-scale page_fault2 # case [1] on a 4 sockets 144 CPU platform, and bisected to it to be # caused by Waiman's optimization (commit bd0b230fe1) of saving one # 'struct page_counter' space for 'struct mem_cgroup'. # # Initially we thought it was due to the cache alignment change introduced # by the patch, but further debug shows that it is due to some hot data # members ('vmstats_local', 'vmstats_percpu', 'vmstats') sit in 2 adjacent # cacheline (2N and 2N+1 cacheline), and when adjacent cache line prefetch # is enabled, it triggers an "extended level" of cache false sharing for # 2 adjacent cache lines. # # So exchange the 2 member blocks, while keeping mostly the original # cache alignment, which can restore and even enhance the performance, # and save 64 bytes of space for 'struct mem_cgroup' (from 2880 to 2816, # with 0day's default RHEL-8.3 kernel config) # # [1]. https://lore.kernel.org/lkml/20201102091543.GM31092@shao2-debian/ # # Fixes: bd0b230fe145 ("mm/memcg: unify swap and memsw page counters") # Reported-by: kernel test robot # Signed-off-by: Feng Tang # Acked-by: Waiman Long # Signed-off-by: Linus Torvalds # < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version # < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-ld --version # < git log --format=%s --max-count=1 4df910620bebb5cfe234af16ac8f6474b60215fd # < make -s -j 48 ARCH=powerpc O=/kisskb/build/linus-rand_powerpc-randconfig_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux- randconfig KCONFIG_SEED=0x8CD6899E # Added to kconfig CONFIG_STANDALONE=y # Added to kconfig CONFIG_BUILD_DOCSRC=n # Added to kconfig CONFIG_MODULE_SIG=n # Added to kconfig CONFIG_CPU_BIG_ENDIAN=y # Added to kconfig CONFIG_PPC64=y # Added to kconfig CONFIG_PPC_DISABLE_WERROR=y # Added to kconfig CONFIG_SECTION_MISMATCH_WARN_ONLY=y # Added to kconfig CONFIG_PREVENT_FIRMWARE_BUILD=y # Added to kconfig CONFIG_CC_STACKPROTECTOR_STRONG=n # Added to kconfig CONFIG_GCC_PLUGINS=n # Added to kconfig CONFIG_LD_HEAD_STUB_CATCH=y # Added to kconfig CONFIG_TRIM_UNUSED_KSYMS=n # Added to kconfig CONFIG_UBSAN=n # < make -s -j 48 ARCH=powerpc O=/kisskb/build/linus-rand_powerpc-randconfig_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux- help # make -s -j 48 ARCH=powerpc O=/kisskb/build/linus-rand_powerpc-randconfig_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux- olddefconfig .config:3940:warning: override: reassigning to symbol SECTION_MISMATCH_WARN_ONLY .config:3941:warning: override: reassigning to symbol PREVENT_FIRMWARE_BUILD .config:3944:warning: override: reassigning to symbol LD_HEAD_STUB_CATCH # make -s -j 48 ARCH=powerpc O=/kisskb/build/linus-rand_powerpc-randconfig_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux- Auto-detecting system features: ... libelf: [ on ] ... zlib: [ on ] ... bpf: [ on ] /usr/bin/env: 'python3': No such file or directory make[4]: *** [Makefile:182: /kisskb/build/linus-rand_powerpc-randconfig_powerpc-gcc4.9/tools/bpf/resolve_btfids/bpf_helper_defs.h] Error 127 make[4]: *** Deleting file '/kisskb/build/linus-rand_powerpc-randconfig_powerpc-gcc4.9/tools/bpf/resolve_btfids/bpf_helper_defs.h' make[3]: *** [Makefile:56: /kisskb/build/linus-rand_powerpc-randconfig_powerpc-gcc4.9/tools/bpf/resolve_btfids//libbpf.a] Error 2 make[3]: *** Waiting for unfinished jobs.... make[2]: *** [Makefile:71: bpf/resolve_btfids] Error 2 make[1]: *** [/kisskb/src/Makefile:1925: tools/bpf/resolve_btfids] Error 2 make[1]: *** Waiting for unfinished jobs.... make: *** [Makefile:185: __sub-make] Error 2 Command 'make -s -j 48 ARCH=powerpc O=/kisskb/build/linus-rand_powerpc-randconfig_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux- ' returned non-zero exit status 2 # rm -rf /kisskb/build/linus-rand_powerpc-randconfig_powerpc-gcc4.9 # Build took: 0:00:09.936371