mirror of
https://github.com/FEX-Emu/linux.git
synced 2024-12-30 21:46:31 +00:00
09ec54429c
The only user of the cycle_last validation is the x86 TSC. In order to
provide NMI safe accessor functions for clock monotonic and
monotonic_raw we need to do that in the core.
We can't do the TSC specific
if (now < cycle_last)
now = cycle_last;
for the other wrapping around clocksources, but TSC has
CLOCKSOURCE_MASK(64) which actually does not mask out anything so if
now is less than cycle_last the subtraction will give a negative
result. So we can check for that in clocksource_delta() and return 0
for that case.
Implement and enable it for x86
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
206 lines
6.4 KiB
Plaintext
206 lines
6.4 KiB
Plaintext
#
|
|
# Timer subsystem related configuration options
|
|
#
|
|
|
|
# Options selectable by arch Kconfig
|
|
|
|
# Watchdog function for clocksources to detect instabilities
|
|
config CLOCKSOURCE_WATCHDOG
|
|
bool
|
|
|
|
# Architecture has extra clocksource data
|
|
config ARCH_CLOCKSOURCE_DATA
|
|
bool
|
|
|
|
# Clocksources require validation of the clocksource against the last
|
|
# cycle update - x86/TSC misfeature
|
|
config CLOCKSOURCE_VALIDATE_LAST_CYCLE
|
|
bool
|
|
|
|
# Timekeeping vsyscall support
|
|
config GENERIC_TIME_VSYSCALL
|
|
bool
|
|
|
|
# Timekeeping vsyscall support
|
|
config GENERIC_TIME_VSYSCALL_OLD
|
|
bool
|
|
|
|
# Old style timekeeping
|
|
config ARCH_USES_GETTIMEOFFSET
|
|
bool
|
|
|
|
# The generic clock events infrastructure
|
|
config GENERIC_CLOCKEVENTS
|
|
bool
|
|
|
|
# Migration helper. Builds, but does not invoke
|
|
config GENERIC_CLOCKEVENTS_BUILD
|
|
bool
|
|
default y
|
|
depends on GENERIC_CLOCKEVENTS
|
|
|
|
# Architecture can handle broadcast in a driver-agnostic way
|
|
config ARCH_HAS_TICK_BROADCAST
|
|
bool
|
|
|
|
# Clockevents broadcasting infrastructure
|
|
config GENERIC_CLOCKEVENTS_BROADCAST
|
|
bool
|
|
depends on GENERIC_CLOCKEVENTS
|
|
|
|
# Automatically adjust the min. reprogramming time for
|
|
# clock event device
|
|
config GENERIC_CLOCKEVENTS_MIN_ADJUST
|
|
bool
|
|
|
|
# Generic update of CMOS clock
|
|
config GENERIC_CMOS_UPDATE
|
|
bool
|
|
|
|
if GENERIC_CLOCKEVENTS
|
|
menu "Timers subsystem"
|
|
|
|
# Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is
|
|
# only related to the tick functionality. Oneshot clockevent devices
|
|
# are supported independ of this.
|
|
config TICK_ONESHOT
|
|
bool
|
|
|
|
config NO_HZ_COMMON
|
|
bool
|
|
depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
|
|
select TICK_ONESHOT
|
|
|
|
choice
|
|
prompt "Timer tick handling"
|
|
default NO_HZ_IDLE if NO_HZ
|
|
|
|
config HZ_PERIODIC
|
|
bool "Periodic timer ticks (constant rate, no dynticks)"
|
|
help
|
|
This option keeps the tick running periodically at a constant
|
|
rate, even when the CPU doesn't need it.
|
|
|
|
config NO_HZ_IDLE
|
|
bool "Idle dynticks system (tickless idle)"
|
|
depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
|
|
select NO_HZ_COMMON
|
|
help
|
|
This option enables a tickless idle system: timer interrupts
|
|
will only trigger on an as-needed basis when the system is idle.
|
|
This is usually interesting for energy saving.
|
|
|
|
Most of the time you want to say Y here.
|
|
|
|
config NO_HZ_FULL
|
|
bool "Full dynticks system (tickless)"
|
|
# NO_HZ_COMMON dependency
|
|
depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
|
|
# We need at least one periodic CPU for timekeeping
|
|
depends on SMP
|
|
# RCU_USER_QS dependency
|
|
depends on HAVE_CONTEXT_TRACKING
|
|
# VIRT_CPU_ACCOUNTING_GEN dependency
|
|
depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
|
|
select NO_HZ_COMMON
|
|
select RCU_USER_QS
|
|
select RCU_NOCB_CPU
|
|
select VIRT_CPU_ACCOUNTING_GEN
|
|
select IRQ_WORK
|
|
help
|
|
Adaptively try to shutdown the tick whenever possible, even when
|
|
the CPU is running tasks. Typically this requires running a single
|
|
task on the CPU. Chances for running tickless are maximized when
|
|
the task mostly runs in userspace and has few kernel activity.
|
|
|
|
You need to fill up the nohz_full boot parameter with the
|
|
desired range of dynticks CPUs.
|
|
|
|
This is implemented at the expense of some overhead in user <-> kernel
|
|
transitions: syscalls, exceptions and interrupts. Even when it's
|
|
dynamically off.
|
|
|
|
Say N.
|
|
|
|
endchoice
|
|
|
|
config NO_HZ_FULL_ALL
|
|
bool "Full dynticks system on all CPUs by default (except CPU 0)"
|
|
depends on NO_HZ_FULL
|
|
help
|
|
If the user doesn't pass the nohz_full boot option to
|
|
define the range of full dynticks CPUs, consider that all
|
|
CPUs in the system are full dynticks by default.
|
|
Note the boot CPU will still be kept outside the range to
|
|
handle the timekeeping duty.
|
|
|
|
config NO_HZ_FULL_SYSIDLE
|
|
bool "Detect full-system idle state for full dynticks system"
|
|
depends on NO_HZ_FULL
|
|
default n
|
|
help
|
|
At least one CPU must keep the scheduling-clock tick running for
|
|
timekeeping purposes whenever there is a non-idle CPU, where
|
|
"non-idle" also includes dynticks CPUs as long as they are
|
|
running non-idle tasks. Because the underlying adaptive-tick
|
|
support cannot distinguish between all CPUs being idle and
|
|
all CPUs each running a single task in dynticks mode, the
|
|
underlying support simply ensures that there is always a CPU
|
|
handling the scheduling-clock tick, whether or not all CPUs
|
|
are idle. This Kconfig option enables scalable detection of
|
|
the all-CPUs-idle state, thus allowing the scheduling-clock
|
|
tick to be disabled when all CPUs are idle. Note that scalable
|
|
detection of the all-CPUs-idle state means that larger systems
|
|
will be slower to declare the all-CPUs-idle state.
|
|
|
|
Say Y if you would like to help debug all-CPUs-idle detection.
|
|
|
|
Say N if you are unsure.
|
|
|
|
config NO_HZ_FULL_SYSIDLE_SMALL
|
|
int "Number of CPUs above which large-system approach is used"
|
|
depends on NO_HZ_FULL_SYSIDLE
|
|
range 1 NR_CPUS
|
|
default 8
|
|
help
|
|
The full-system idle detection mechanism takes a lazy approach
|
|
on large systems, as is required to attain decent scalability.
|
|
However, on smaller systems, scalability is not anywhere near as
|
|
large a concern as is energy efficiency. The sysidle subsystem
|
|
therefore uses a fast but non-scalable algorithm for small
|
|
systems and a lazier but scalable algorithm for large systems.
|
|
This Kconfig parameter defines the number of CPUs in the largest
|
|
system that will be considered to be "small".
|
|
|
|
The default value will be fine in most cases. Battery-powered
|
|
systems that (1) enable NO_HZ_FULL_SYSIDLE, (2) have larger
|
|
numbers of CPUs, and (3) are suffering from battery-lifetime
|
|
problems due to long sysidle latencies might wish to experiment
|
|
with larger values for this Kconfig parameter. On the other
|
|
hand, they might be even better served by disabling NO_HZ_FULL
|
|
entirely, given that NO_HZ_FULL is intended for HPC and
|
|
real-time workloads that at present do not tend to be run on
|
|
battery-powered systems.
|
|
|
|
Take the default if you are unsure.
|
|
|
|
config NO_HZ
|
|
bool "Old Idle dynticks config"
|
|
depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
|
|
help
|
|
This is the old config entry that enables dynticks idle.
|
|
We keep it around for a little while to enforce backward
|
|
compatibility with older config files.
|
|
|
|
config HIGH_RES_TIMERS
|
|
bool "High Resolution Timer Support"
|
|
depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
|
|
select TICK_ONESHOT
|
|
help
|
|
This option enables high resolution timer support. If your
|
|
hardware is not capable then this option only increases
|
|
the size of the kernel image.
|
|
|
|
endmenu
|
|
endif
|