I am sponsoring the following fasttrack for Gerry Liu from Intel. It
proposes a notification interface initially used and provided by memory
power management work done by Intel engineers in the OpenSolaris
Tesla project.
It requests micro/patch release binding. All interfaces will have
a "Volatile" stability. Timeout is February 25th.
This project, release binding, and stability has been reviewed and
approved by the OpenSolaris Tesla project leaders and contributors.
1. Introduction
1.1. Project/Component Working Name:
CPU idle notification interface
1.2. Name of Document Author/Supplier:
Author: Gerry Liu <jiang.liu at intel.com>
1.3. Date of This Document:
November 16, 2008
4. Technical Description:
4.1. Problem
A CPU idle notification mechanism is needed to signal other
components which are interested in the CPU idle state change events
when CPU enters/exits idle state. This mechanism could be used by
following components:
A) Memory power saving driver
B) Lazy TLB flush on x86 system
C) CPU power management framework
4.2. Proposal
We propose to add following data structures/interfaces to
OpenSolaris kernel.
4.2.1 CPU idle notification information data structure
typedef struct cpu_idle_info {
int ci_flags;
int ci_intr_count; /* Interrupt count. */
int ci_idle_state; /* Idle state to enter. */
hrtime_t ci_idle_latency; /* Idle round trip latency. */
hrtime_t ci_max_idle_time; /* Predicted max idle time. */
hrtime_t ci_last_idle_time;/* Last idle period. */
hrtime_t ci_last_busy_time;/* Last busy period. */
} cpu_idle_info_t;
This structure is used to pass CPU idle information to callbacks.
It could be extended to support architecture/platform specific
information in future.
Valid flags for cpu_idle_info_t:
CPU_IDLE_CI_FLAG_IDLE_STATE: field ci_idle_state is valid.
CPU_IDLE_CI_FLAG_IDLE_LATENCY: field ci_idle_latency is valid.
CPU_IDLE_CB_FLAG_MAX_IDLE_TIME: field ci_max_idle_time is valid.
4.2.2 Prototype of entering idle state notification callback
typedef void (*cpu_idle_enter_cbfn)(void *arg,
cpu_idle_info_t *infop);
Entering idle state notification callback must obey all constraints
which applies to idle thread becuase it will be called in idle
thread context.
Argument arg is the parameter passed in when registering callback.
4.2.3 Prototype of exiting idle state notification callback
typedef void (*cpu_idle_exit_cbfn)(void *arg, int flags);
Exiting idle state notification callback will be called in idle
thread context or interrupt context. There are flags to distinguish
the calling contexts.
arg is the parameter passed in when registering callback.
Valid flags for exiting idle state notification callback:
CPU_IDLE_CB_FLAG_INTR: called in interrupt context
CPU_IDLE_CB_FLAG_IDLE: called in idle thread context
4.2.4 CPU idle notification callback data structures
typedef struct cpu_idle_callback {
int version;
cpu_idle_enter_cbfn idle_enter;
cpu_idle_exit_cbfn idle_exit;
} cpu_idle_callback_t;
At least one of idle_enter and idle_exit is non-NULL.
4.2.5. Register CPU idle notification callback
int cpu_idle_register_callback(uint_t priority,
cpu_idle_callback_t *callbackp, void *arg, void **hdlpp);
This interface registers a callback to be called when CPU idle state
changes. All registered callbacks will be called in priority order
from high to low when CPU enters idle state and will be called in
reverse order when CPU exits idle state.
Argument priority is used to determine the calling order of
registered callbacks.
Argument arg will be passed back to registered callback and how to
use it is determined by callback.
4.2.6. Deregister CPU notification callback
int cpu_idle_unregister_callback(uint_t priority,
cpu_idle_callback_t *callbackp, void *arg, void *hdlp);
This interface deregisters a registered callback.
4.2.7. Signal entering idle state event
void cpu_idle_enter(cpu_idle_info_t *infop);
This interface notifies idle notification subsystem that a specific
CPU is entering into idle state.
4.2.8. Signal exiting idle state event
void cpu_idle_exit(int flags);
This interface notifies idle notification subsystem that a specific
CPU is exiting from idle state.
6. Resources and Schedule:
6.4. Steering Committee requested information
6.4.1. Consolidation C-team Name:
ON
6.5. ARC review type: FastTrack
6.6. ARC Exposure: open
