> Subject: [PATCH v6 09/10] arm64: support cpuidle-haltpoll > > Add architectural support for cpuidle-haltpoll driver by defining > arch_haltpoll_*(). > > Also define ARCH_CPUIDLE_HALTPOLL to allow cpuidle-haltpoll to be > selected, and given that we have an optimized polling mechanism > in smp_cond_load*(), select ARCH_HAS_OPTIMIZED_POLL. > > smp_cond_load*() are implemented via LDXR, WFE, with LDXR loading > a memory region in exclusive state and the WFE waiting for any > stores to it. > > In the edge case -- no CPU stores to the waited region and there's no > interrupt -- the event-stream will provide the terminating condition > ensuring we don't wait forever, but because the event-stream runs at > a fixed frequency (configured at 10kHz) we might spend more time in > the polling stage than specified by cpuidle_poll_time(). > > This would only happen in the last iteration, since overshooting the > poll_limit means the governor moves out of the polling stage. > > Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx> > --- > arch/arm64/Kconfig | 10 ++++++++++ > arch/arm64/include/asm/cpuidle_haltpoll.h | 9 +++++++++ > arch/arm64/kernel/cpuidle.c | 23 +++++++++++++++++++++++ FYI, arch/arm64/kernel/cpuidle.c is move to drivers/acpi/arm64/ in 6.11 and therefore I couldn't apply the series to 6.11. https://github.com/torvalds/linux/commit/99e7a8adc0ca906151f5d70ff68b8a81f53fd106 Regards, Tomohiro Misono > 3 files changed, 42 insertions(+) > create mode 100644 arch/arm64/include/asm/cpuidle_haltpoll.h > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 5d91259ee7b5..cf1c6681eb0a 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -35,6 +35,7 @@ config ARM64 > select ARCH_HAS_MEMBARRIER_SYNC_CORE > select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS > select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE > + select ARCH_HAS_OPTIMIZED_POLL > select ARCH_HAS_PTE_DEVMAP > select ARCH_HAS_PTE_SPECIAL > select ARCH_HAS_HW_PTE_YOUNG > @@ -2376,6 +2377,15 @@ config ARCH_HIBERNATION_HEADER > config ARCH_SUSPEND_POSSIBLE > def_bool y > > +config ARCH_CPUIDLE_HALTPOLL > + bool "Enable selection of the cpuidle-haltpoll driver" > + default n > + help > + cpuidle-haltpoll allows for adaptive polling based on > + current load before entering the idle state. > + > + Some virtualized workloads benefit from using it. > + > endmenu # "Power management options" > > menu "CPU Power Management" > diff --git a/arch/arm64/include/asm/cpuidle_haltpoll.h b/arch/arm64/include/asm/cpuidle_haltpoll.h > new file mode 100644 > index 000000000000..65f289407a6c > --- /dev/null > +++ b/arch/arm64/include/asm/cpuidle_haltpoll.h > @@ -0,0 +1,9 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef _ARCH_HALTPOLL_H > +#define _ARCH_HALTPOLL_H > + > +static inline void arch_haltpoll_enable(unsigned int cpu) { } > +static inline void arch_haltpoll_disable(unsigned int cpu) { } > + > +bool arch_haltpoll_want(bool force); > +#endif > diff --git a/arch/arm64/kernel/cpuidle.c b/arch/arm64/kernel/cpuidle.c > index f372295207fb..334df82a0eac 100644 > --- a/arch/arm64/kernel/cpuidle.c > +++ b/arch/arm64/kernel/cpuidle.c > @@ -72,3 +72,26 @@ __cpuidle int acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi) > lpi->index, state); > } > #endif > + > +#if IS_ENABLED(CONFIG_HALTPOLL_CPUIDLE) > + > +#include <asm/cpuidle_haltpoll.h> > + > +bool arch_haltpoll_want(bool force) > +{ > + /* > + * Enabling haltpoll requires two things: > + * > + * - Event stream support to provide a terminating condition to the > + * WFE in the poll loop. > + * > + * - KVM support for arch_haltpoll_enable(), arch_haltpoll_enable(). > + * > + * Given that the second is missing, allow haltpoll to only be force > + * loaded. > + */ > + return (arch_timer_evtstrm_available() && false) || force; > +} > + > +EXPORT_SYMBOL_GPL(arch_haltpoll_want); > +#endif > -- > 2.43.5
