** Description changed: [Impact] Performance is lowered for ARM >= v8.1 cpus by not taking advantage of the "Large System Extenstion" atomic instructions they provide. Note: This config was enabled during xenial development, but was disabled to workaround a FTBFS[*] due to us not having a new enough binutils to support it. binutils was later updated in xenial, and supports these instructions. [Test Case] - TBD + grep CONFIG_ARM64_LSE_ATOMICS=y /boot/config-$(uname -r) [Regression Risk] - There is a known small performance overhead for <= ARMv8.1 arm64 systems (noted in the Kconfig). - [...TBD...] + There is a known small performance overhead for < ARMv8.1 arm64 systems (noted in the Kconfig). To mitigate the risk of runtime or build failures, this should be tested on both ARMv8 and >= ARMv8.1 systems. [*] https://answers.launchpad.net/~canonical-kernel- team/+archive/ubuntu/unstable/+build/8438034
** Description changed: [Impact] Performance is lowered for ARM >= v8.1 cpus by not taking advantage of the "Large System Extenstion" atomic instructions they provide. Note: This config was enabled during xenial development, but was disabled to workaround a FTBFS[*] due to us not having a new enough binutils to support it. binutils was later updated in xenial, and supports these instructions. [Test Case] grep CONFIG_ARM64_LSE_ATOMICS=y /boot/config-$(uname -r) [Regression Risk] - There is a known small performance overhead for < ARMv8.1 arm64 systems (noted in the Kconfig). To mitigate the risk of runtime or build failures, this should be tested on both ARMv8 and >= ARMv8.1 systems. + There is a known small performance overhead for < ARMv8.1 arm64 systems (noted in the Kconfig). To mitigate the risk of runtime or build failures, this should be tested on both ARMv8 and >= ARMv8.1 systems, to exercise both code paths. [*] https://answers.launchpad.net/~canonical-kernel- team/+archive/ubuntu/unstable/+build/8438034 -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1691614 Title: please enable CONFIG_ARM64_LSE_ATOMICS Status in linux package in Ubuntu: Incomplete Status in linux source package in Xenial: Incomplete Status in linux source package in Yakkety: Incomplete Status in linux source package in Zesty: Incomplete Bug description: [Impact] Performance is lowered for ARM >= v8.1 cpus by not taking advantage of the "Large System Extenstion" atomic instructions they provide. Note: This config was enabled during xenial development, but was disabled to workaround a FTBFS[*] due to us not having a new enough binutils to support it. binutils was later updated in xenial, and supports these instructions. [Test Case] grep CONFIG_ARM64_LSE_ATOMICS=y /boot/config-$(uname -r) [Regression Risk] There is a known small performance overhead for < ARMv8.1 arm64 systems (noted in the Kconfig). To mitigate the risk of runtime or build failures, this should be tested on both ARMv8 and >= ARMv8.1 systems, to exercise both code paths. [*] https://answers.launchpad.net/~canonical-kernel- team/+archive/ubuntu/unstable/+build/8438034 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1691614/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
