# git rev-parse -q --verify 6a4746ba06191e23d30230738e94334b26590a8a^{commit}
# git fetch -q -n -f git://fs.ozlabs.ibm.com/kernel/linus master
# git rev-parse -q --verify 6a4746ba06191e23d30230738e94334b26590a8a^{commit}
6a4746ba06191e23d30230738e94334b26590a8a
# git checkout -q -f -B kisskb 6a4746ba06191e23d30230738e94334b26590a8a
# git clean -qxdf
# < git log -1
# commit 6a4746ba06191e23d30230738e94334b26590a8a
# Author: Vasily Averin <vvs@virtuozzo.com>
# Date:   Sat Sep 11 10:40:08 2021 +0300
# 
#     ipc: remove memcg accounting for sops objects in do_semtimedop()
#     
#     Linus proposes to revert an accounting for sops objects in
#     do_semtimedop() because it's really just a temporary buffer
#     for a single semtimedop() system call.
#     
#     This object can consume up to 2 pages, syscall is sleeping
#     one, size and duration can be controlled by user, and this
#     allocation can be repeated by many thread at the same time.
#     
#     However Shakeel Butt pointed that there are much more popular
#     objects with the same life time and similar memory
#     consumption, the accounting of which was decided to be
#     rejected for performance reasons.
#     
#     Considering at least 2 pages for task_struct and 2 pages for
#     the kernel stack, a back of the envelope calculation gives a
#     footprint amplification of <1.5 so this temporal buffer can be
#     safely ignored.
#     
#     The factor would IMO be interesting if it was >> 2 (from the
#     PoV of excessive (ab)use, fine-grained accounting seems to be
#     currently unfeasible due to performance impact).
#     
#     Link: https://lore.kernel.org/lkml/90e254df-0dfe-f080-011e-b7c53ee7fd20@virtuozzo.com/
#     Fixes: 18319498fdd4 ("memcg: enable accounting of ipc resources")
#     Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
#     Acked-by: Michal Hocko <mhocko@suse.com>
#     Reviewed-by: Michal Koutný <mkoutny@suse.com>
#     Acked-by: Shakeel Butt <shakeelb@google.com>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-ld --version
# < git log --format=%s --max-count=1 6a4746ba06191e23d30230738e94334b26590a8a
# < make -s -j 80 ARCH=arm64 O=/kisskb/build/linus-rand_arm64-randconfig_arm64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-  randconfig
# Added to kconfig CONFIG_PREVENT_FIRMWARE_BUILD=y
# < make -s -j 80 ARCH=arm64 O=/kisskb/build/linus-rand_arm64-randconfig_arm64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-  help
# make -s -j 80 ARCH=arm64 O=/kisskb/build/linus-rand_arm64-randconfig_arm64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-  olddefconfig
# make -s -j 80 ARCH=arm64 O=/kisskb/build/linus-rand_arm64-randconfig_arm64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-  
/kisskb/src/scripts/dtc/include-prefixes/arm/bcm2711-rpi-4-b.dts:220.10-231.4: Warning (pci_device_reg): /scb/pcie@7d500000/pci@1,0: PCI unit address format error, expected "0,0"
/kisskb/src/scripts/dtc/include-prefixes/arm/bcm2711-rpi-4-b.dts:220.10-231.4: Warning (pci_device_reg): /scb/pcie@7d500000/pci@1,0: PCI unit address format error, expected "0,0"
Completed OK
# rm -rf /kisskb/build/linus-rand_arm64-randconfig_arm64-gcc8
# Build took: 0:05:57.694554