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| author | Marcelo Tosatti <mtosatti@redhat.com> | 2019-07-04 01:51:28 +0200 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2019-07-30 17:27:37 +0200 |
| commit | 2cffe9f6b96fece065ee8522673c90e92ef2085d (patch) | |
| tree | 9d8f97f6710e7abfd7698705ba75bad51401be6f /drivers/cpuidle/Kconfig | |
| parent | governors: unify last_state_idx (diff) | |
| download | linux-2cffe9f6b96fece065ee8522673c90e92ef2085d.tar.xz linux-2cffe9f6b96fece065ee8522673c90e92ef2085d.zip | |
cpuidle: add haltpoll governor
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>
Diffstat (limited to 'drivers/cpuidle/Kconfig')
| -rw-r--r-- | drivers/cpuidle/Kconfig | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/drivers/cpuidle/Kconfig b/drivers/cpuidle/Kconfig index cc8efc56be7d..88727b7c0d59 100644 --- a/drivers/cpuidle/Kconfig +++ b/drivers/cpuidle/Kconfig @@ -33,6 +33,17 @@ config CPU_IDLE_GOV_TEO Some workloads benefit from using it and it generally should be safe to use. Say Y here if you are not happy with the alternatives. +config CPU_IDLE_GOV_HALTPOLL + bool "Haltpoll governor (for virtualized systems)" + depends on KVM_GUEST + help + This governor implements haltpoll idle state selection, to be + used in conjunction with the haltpoll cpuidle driver, allowing + for polling for a certain amount of time before entering idle + state. + + Some virtualized workloads benefit from using it. + config DT_IDLE_STATES bool |