| Message ID | 20240925232425.2763385-12-ankur.a.arora@oracle.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Enable haltpoll on arm64 | expand |
On Wed, 2024-09-25 at 16:24 -0700, Ankur Arora wrote: > CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe. > > > > Add architectural support for the cpuidle-haltpoll driver by defining > arch_haltpoll_*(). Also define ARCH_CPUIDLE_HALTPOLL to allow > cpuidle-haltpoll to be selected. > > Haltpoll uses poll_idle() to do the actual polling. This in turn > uses smp_cond_load*() to wait until there's a specific store to > a cacheline. > In the edge case -- no stores to the cacheline and no interrupt -- > the event-stream provides the terminating condition ensuring we > don't wait forever. But because the event-stream runs at a fixed > frequency (configured at 10kHz) haltpoll 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 will move out of the polling stage. > > Tested-by: Haris Okanovic <harisokn@amazon.com> > Tested-by: Misono Tomohiro <misono.tomohiro@fujitsu.com> > Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com> > --- > arch/arm64/Kconfig | 6 ++++++ > arch/arm64/include/asm/cpuidle_haltpoll.h | 24 +++++++++++++++++++++++ > 2 files changed, 30 insertions(+) > create mode 100644 arch/arm64/include/asm/cpuidle_haltpoll.h > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index ef9c22c3cff2..5fc99eba22b2 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -2415,6 +2415,12 @@ config ARCH_HIBERNATION_HEADER > config ARCH_SUSPEND_POSSIBLE > def_bool y > > +config ARCH_CPUIDLE_HALTPOLL > + bool "Enable selection of the cpuidle-haltpoll driver" > + help > + cpuidle-haltpoll allows for adaptive polling based on > + current load before entering the idle state. > + > 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..91f0be707629 > --- /dev/null > +++ b/arch/arm64/include/asm/cpuidle_haltpoll.h > @@ -0,0 +1,24 @@ > +/* 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) { } > + > +static inline 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_disable(). > + * > + * Given that the second is missing, only allow force loading for > + * haltpoll. > + */ > + return force; > +} > +#endif > -- > 2.43.5 > I applied your patches to master e32cde8d2bd7 and verified same performance gains on AWS Graviton. Reviewed-by: Haris Okanovic <harisokn@amazon.com> Tested-by: Haris Okanovic <harisokn@amazon.com>
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index ef9c22c3cff2..5fc99eba22b2 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -2415,6 +2415,12 @@ config ARCH_HIBERNATION_HEADER config ARCH_SUSPEND_POSSIBLE def_bool y +config ARCH_CPUIDLE_HALTPOLL + bool "Enable selection of the cpuidle-haltpoll driver" + help + cpuidle-haltpoll allows for adaptive polling based on + current load before entering the idle state. + 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..91f0be707629 --- /dev/null +++ b/arch/arm64/include/asm/cpuidle_haltpoll.h @@ -0,0 +1,24 @@ +/* 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) { } + +static inline 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_disable(). + * + * Given that the second is missing, only allow force loading for + * haltpoll. + */ + return force; +} +#endif