On 2020-09-29 10:17, Jingyi Wang wrote:
TWE Delay is an optional feature in ARMv8.6 Extentions. There is a
performance benefit in waiting for a period of time for an event to
arrive before taking the trap as it is common that event will arrive
“quite soon” after executing the WFE instruction.
Define "quite soon". Quantify "performance benefits". Which are the
workloads that actually benefit from this imitation of the x86 PLE?
I was opposed to this when the spec was drafted, and I still am given
that there is zero supporting evidence that it bring any gain over
immediate trapping in an oversubscribed environment (which is the only
case where it matters).
Thanks,
M.
This series adds support for TWED feature and implements TWE delay
value dynamic adjustment.
Thanks for Shameer's advice on this series. The function of this patch
has been tested on TWED supported hardware and the performance of it is
still on test, any advice will be welcomed.
Jingyi Wang (2):
KVM: arm64: Make use of TWED feature
KVM: arm64: Use dynamic TWE Delay value
Zengruan Ye (2):
arm64: cpufeature: TWED support detection
KVM: arm64: Add trace for TWED update
arch/arm64/Kconfig | 10 +++++
arch/arm64/include/asm/cpucaps.h | 3 +-
arch/arm64/include/asm/kvm_arm.h | 5 +++
arch/arm64/include/asm/kvm_emulate.h | 38 ++++++++++++++++++
arch/arm64/include/asm/kvm_host.h | 19 ++++++++-
arch/arm64/include/asm/virt.h | 8 ++++
arch/arm64/kernel/cpufeature.c | 12 ++++++
arch/arm64/kvm/arm.c | 58 ++++++++++++++++++++++++++++
arch/arm64/kvm/handle_exit.c | 2 +
arch/arm64/kvm/trace_arm.h | 21 ++++++++++
10 files changed, 174 insertions(+), 2 deletions(-)
--
Jazz is not dead. It just smells funny...
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