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The cpuidle_haltpoll governor, in conjunction with the haltpoll cpuidle
driver, allows guest vcpus to poll for a specified amount of time before
halting.
This provides the following benefits to host side polling:
1) The POLL flag is set while polling is performed, which allows
a remote vCPU to avoid sending an IPI (and the associated
cost of handling the IPI) when performing a wakeup.
2) The VM-exit cost can be avoided.
The downside of guest side polling is that polling is performed
even with other runnable tasks in the host.
Results comparing halt_poll_ns and server/client application
where a small packet is ping-ponged:
host --> 31.33
halt_poll_ns=300000 / no guest busy spin --> 33.40 (93.8%)
halt_poll_ns=0 / guest_halt_poll_ns=300000 --> 32.73 (95.7%)
For the SAP HANA benchmarks (where idle_spin is a parameter
of the previous version of the patch, results should be the
same):
hpns == halt_poll_ns
idle_spin=0/ idle_spin=800/ idle_spin=0/
hpns=200000 hpns=0 hpns=800000
DeleteC06T03 (100 thread) 1.76 1.71 (-3%) 1.78 (+1%)
InsertC16T02 (100 thread) 2.14 2.07 (-3%) 2.18 (+1.8%)
DeleteC00T01 (1 thread) 1.34 1.28 (-4.5%) 1.29 (-3.7%)
UpdateC00T03 (1 thread) 4.72 4.18 (-12%) 4.53 (-5%)
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
79 lines
2.1 KiB
Plaintext
79 lines
2.1 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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menu "CPU Idle"
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config CPU_IDLE
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bool "CPU idle PM support"
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default y if ACPI || PPC_PSERIES
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select CPU_IDLE_GOV_LADDER if (!NO_HZ && !NO_HZ_IDLE)
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select CPU_IDLE_GOV_MENU if (NO_HZ || NO_HZ_IDLE) && !CPU_IDLE_GOV_TEO
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help
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CPU idle is a generic framework for supporting software-controlled
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idle processor power management. It includes modular cross-platform
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governors that can be swapped during runtime.
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If you're using an ACPI-enabled platform, you should say Y here.
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if CPU_IDLE
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config CPU_IDLE_MULTIPLE_DRIVERS
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bool
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config CPU_IDLE_GOV_LADDER
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bool "Ladder governor (for periodic timer tick)"
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config CPU_IDLE_GOV_MENU
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bool "Menu governor (for tickless system)"
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config CPU_IDLE_GOV_TEO
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bool "Timer events oriented (TEO) governor (for tickless systems)"
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help
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This governor implements a simplified idle state selection method
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focused on timer events and does not do any interactivity boosting.
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Some workloads benefit from using it and it generally should be safe
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to use. Say Y here if you are not happy with the alternatives.
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config CPU_IDLE_GOV_HALTPOLL
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bool "Haltpoll governor (for virtualized systems)"
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depends on KVM_GUEST
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help
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This governor implements haltpoll idle state selection, to be
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used in conjunction with the haltpoll cpuidle driver, allowing
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for polling for a certain amount of time before entering idle
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state.
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Some virtualized workloads benefit from using it.
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config DT_IDLE_STATES
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bool
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menu "ARM CPU Idle Drivers"
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depends on ARM || ARM64
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source "drivers/cpuidle/Kconfig.arm"
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endmenu
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menu "MIPS CPU Idle Drivers"
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depends on MIPS
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source "drivers/cpuidle/Kconfig.mips"
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endmenu
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menu "POWERPC CPU Idle Drivers"
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depends on PPC
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source "drivers/cpuidle/Kconfig.powerpc"
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endmenu
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config HALTPOLL_CPUIDLE
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tristate "Halt poll cpuidle driver"
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depends on X86 && KVM_GUEST
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default y
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help
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This option enables halt poll cpuidle driver, which allows to poll
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before halting in the guest (more efficient than polling in the
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host via halt_poll_ns for some scenarios).
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endif
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config ARCH_NEEDS_CPU_IDLE_COUPLED
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def_bool n
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endmenu
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