# 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 <feng.tang@intel.com>
# 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 <rong.a.chen@intel.com>
#     Signed-off-by: Feng Tang <feng.tang@intel.com>
#     Acked-by: Waiman Long <longman@redhat.com>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /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 24 ARCH=powerpc O=/kisskb/build/linus_pseries_defconfig+POWERNV=n_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-  pseries_defconfig
# Added to kconfig CONFIG_PPC_POWERNV=n
# < make -s -j 24 ARCH=powerpc O=/kisskb/build/linus_pseries_defconfig+POWERNV=n_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-  help
# make -s -j 24 ARCH=powerpc O=/kisskb/build/linus_pseries_defconfig+POWERNV=n_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-  olddefconfig
# make -s -j 24 ARCH=powerpc O=/kisskb/build/linus_pseries_defconfig+POWERNV=n_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-  
/kisskb/src/fs/btrfs/tree-checker.c: In function 'check_root_item':
/kisskb/src/fs/btrfs/tree-checker.c:1056:9: warning: missing braces around initializer [-Wmissing-braces]
  struct btrfs_root_item ri = { 0 };
         ^
/kisskb/src/fs/btrfs/tree-checker.c:1056:9: warning: (near initialization for 'ri.inode') [-Wmissing-braces]
/kisskb/src/drivers/net/ethernet/chelsio/cxgb4/sge.c: In function 'cxgb4_write_partial_sgl':
/kisskb/src/drivers/net/ethernet/chelsio/cxgb4/sge.c:910:9: warning: missing braces around initializer [-Wmissing-braces]
  struct ulptx_sge_pair buf[MAX_SKB_FRAGS / 2 + 1] = {0}, *to;
         ^
/kisskb/src/drivers/net/ethernet/chelsio/cxgb4/sge.c:910:9: warning: (near initialization for 'buf[0]') [-Wmissing-braces]
Completed OK
# rm -rf /kisskb/build/linus_pseries_defconfig+POWERNV=n_powerpc-gcc4.9
# Build took: 0:03:41.838753