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![Nicholas Piggin](/assets/img/avatar_default.png)
Patch series "mm: remove quicklist page table caches". A while ago Nicholas proposed to remove quicklist page table caches [1]. I've rebased his patch on the curren upstream and switched ia64 and sh to use generic versions of PTE allocation. [1] https://lore.kernel.org/linux-mm/20190711030339.20892-1-npiggin@gmail.com This patch (of 3): Remove page table allocator "quicklists". These have been around for a long time, but have not got much traction in the last decade and are only used on ia64 and sh architectures. The numbers in the initial commit look interesting but probably don't apply anymore. If anybody wants to resurrect this it's in the git history, but it's unhelpful to have this code and divergent allocator behaviour for minor archs. Also it might be better to instead make more general improvements to page allocator if this is still so slow. Link: http://lkml.kernel.org/r/1565250728-21721-2-git-send-email-rppt@linux.ibm.com Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
474 lines
11 KiB
C
474 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Generic entry points for the idle threads and
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* implementation of the idle task scheduling class.
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*
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* (NOTE: these are not related to SCHED_IDLE batch scheduled
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* tasks which are handled in sched/fair.c )
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*/
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#include "sched.h"
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#include <trace/events/power.h>
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/* Linker adds these: start and end of __cpuidle functions */
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extern char __cpuidle_text_start[], __cpuidle_text_end[];
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/**
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* sched_idle_set_state - Record idle state for the current CPU.
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* @idle_state: State to record.
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*/
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void sched_idle_set_state(struct cpuidle_state *idle_state)
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{
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idle_set_state(this_rq(), idle_state);
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}
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static int __read_mostly cpu_idle_force_poll;
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void cpu_idle_poll_ctrl(bool enable)
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{
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if (enable) {
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cpu_idle_force_poll++;
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} else {
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cpu_idle_force_poll--;
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WARN_ON_ONCE(cpu_idle_force_poll < 0);
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}
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}
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#ifdef CONFIG_GENERIC_IDLE_POLL_SETUP
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static int __init cpu_idle_poll_setup(char *__unused)
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{
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cpu_idle_force_poll = 1;
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return 1;
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}
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__setup("nohlt", cpu_idle_poll_setup);
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static int __init cpu_idle_nopoll_setup(char *__unused)
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{
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cpu_idle_force_poll = 0;
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return 1;
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}
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__setup("hlt", cpu_idle_nopoll_setup);
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#endif
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static noinline int __cpuidle cpu_idle_poll(void)
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{
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rcu_idle_enter();
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trace_cpu_idle_rcuidle(0, smp_processor_id());
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local_irq_enable();
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stop_critical_timings();
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while (!tif_need_resched() &&
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(cpu_idle_force_poll || tick_check_broadcast_expired()))
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cpu_relax();
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start_critical_timings();
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trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
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rcu_idle_exit();
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return 1;
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}
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/* Weak implementations for optional arch specific functions */
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void __weak arch_cpu_idle_prepare(void) { }
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void __weak arch_cpu_idle_enter(void) { }
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void __weak arch_cpu_idle_exit(void) { }
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void __weak arch_cpu_idle_dead(void) { }
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void __weak arch_cpu_idle(void)
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{
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cpu_idle_force_poll = 1;
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local_irq_enable();
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}
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/**
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* default_idle_call - Default CPU idle routine.
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*
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* To use when the cpuidle framework cannot be used.
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*/
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void __cpuidle default_idle_call(void)
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{
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if (current_clr_polling_and_test()) {
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local_irq_enable();
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} else {
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stop_critical_timings();
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arch_cpu_idle();
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start_critical_timings();
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}
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}
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static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
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int next_state)
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{
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/*
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* The idle task must be scheduled, it is pointless to go to idle, just
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* update no idle residency and return.
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*/
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if (current_clr_polling_and_test()) {
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dev->last_residency = 0;
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local_irq_enable();
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return -EBUSY;
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}
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/*
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* Enter the idle state previously returned by the governor decision.
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* This function will block until an interrupt occurs and will take
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* care of re-enabling the local interrupts
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*/
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return cpuidle_enter(drv, dev, next_state);
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}
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/**
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* cpuidle_idle_call - the main idle function
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*
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* NOTE: no locks or semaphores should be used here
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*
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* On archs that support TIF_POLLING_NRFLAG, is called with polling
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* set, and it returns with polling set. If it ever stops polling, it
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* must clear the polling bit.
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*/
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static void cpuidle_idle_call(void)
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{
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struct cpuidle_device *dev = cpuidle_get_device();
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struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
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int next_state, entered_state;
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/*
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* Check if the idle task must be rescheduled. If it is the
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* case, exit the function after re-enabling the local irq.
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*/
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if (need_resched()) {
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local_irq_enable();
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return;
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}
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/*
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* The RCU framework needs to be told that we are entering an idle
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* section, so no more rcu read side critical sections and one more
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* step to the grace period
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*/
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if (cpuidle_not_available(drv, dev)) {
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tick_nohz_idle_stop_tick();
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rcu_idle_enter();
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default_idle_call();
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goto exit_idle;
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}
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/*
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* Suspend-to-idle ("s2idle") is a system state in which all user space
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* has been frozen, all I/O devices have been suspended and the only
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* activity happens here and in iterrupts (if any). In that case bypass
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* the cpuidle governor and go stratight for the deepest idle state
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* available. Possibly also suspend the local tick and the entire
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* timekeeping to prevent timer interrupts from kicking us out of idle
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* until a proper wakeup interrupt happens.
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*/
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if (idle_should_enter_s2idle() || dev->use_deepest_state) {
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if (idle_should_enter_s2idle()) {
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rcu_idle_enter();
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entered_state = cpuidle_enter_s2idle(drv, dev);
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if (entered_state > 0) {
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local_irq_enable();
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goto exit_idle;
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}
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rcu_idle_exit();
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}
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tick_nohz_idle_stop_tick();
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rcu_idle_enter();
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next_state = cpuidle_find_deepest_state(drv, dev);
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call_cpuidle(drv, dev, next_state);
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} else {
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bool stop_tick = true;
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/*
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* Ask the cpuidle framework to choose a convenient idle state.
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*/
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next_state = cpuidle_select(drv, dev, &stop_tick);
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if (stop_tick || tick_nohz_tick_stopped())
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tick_nohz_idle_stop_tick();
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else
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tick_nohz_idle_retain_tick();
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rcu_idle_enter();
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entered_state = call_cpuidle(drv, dev, next_state);
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/*
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* Give the governor an opportunity to reflect on the outcome
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*/
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cpuidle_reflect(dev, entered_state);
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}
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exit_idle:
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__current_set_polling();
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/*
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* It is up to the idle functions to reenable local interrupts
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*/
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if (WARN_ON_ONCE(irqs_disabled()))
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local_irq_enable();
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rcu_idle_exit();
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}
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/*
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* Generic idle loop implementation
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*
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* Called with polling cleared.
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*/
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static void do_idle(void)
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{
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int cpu = smp_processor_id();
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/*
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* If the arch has a polling bit, we maintain an invariant:
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*
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* Our polling bit is clear if we're not scheduled (i.e. if rq->curr !=
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* rq->idle). This means that, if rq->idle has the polling bit set,
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* then setting need_resched is guaranteed to cause the CPU to
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* reschedule.
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*/
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__current_set_polling();
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tick_nohz_idle_enter();
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while (!need_resched()) {
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rmb();
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local_irq_disable();
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if (cpu_is_offline(cpu)) {
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tick_nohz_idle_stop_tick();
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cpuhp_report_idle_dead();
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arch_cpu_idle_dead();
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}
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arch_cpu_idle_enter();
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/*
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* In poll mode we reenable interrupts and spin. Also if we
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* detected in the wakeup from idle path that the tick
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* broadcast device expired for us, we don't want to go deep
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* idle as we know that the IPI is going to arrive right away.
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*/
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if (cpu_idle_force_poll || tick_check_broadcast_expired()) {
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tick_nohz_idle_restart_tick();
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cpu_idle_poll();
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} else {
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cpuidle_idle_call();
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}
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arch_cpu_idle_exit();
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}
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/*
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* Since we fell out of the loop above, we know TIF_NEED_RESCHED must
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* be set, propagate it into PREEMPT_NEED_RESCHED.
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*
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* This is required because for polling idle loops we will not have had
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* an IPI to fold the state for us.
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*/
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preempt_set_need_resched();
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tick_nohz_idle_exit();
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__current_clr_polling();
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/*
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* We promise to call sched_ttwu_pending() and reschedule if
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* need_resched() is set while polling is set. That means that clearing
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* polling needs to be visible before doing these things.
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*/
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smp_mb__after_atomic();
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sched_ttwu_pending();
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schedule_idle();
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if (unlikely(klp_patch_pending(current)))
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klp_update_patch_state(current);
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}
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bool cpu_in_idle(unsigned long pc)
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{
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return pc >= (unsigned long)__cpuidle_text_start &&
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pc < (unsigned long)__cpuidle_text_end;
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}
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struct idle_timer {
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struct hrtimer timer;
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int done;
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};
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static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer)
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{
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struct idle_timer *it = container_of(timer, struct idle_timer, timer);
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WRITE_ONCE(it->done, 1);
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set_tsk_need_resched(current);
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return HRTIMER_NORESTART;
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}
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void play_idle(unsigned long duration_us)
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{
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struct idle_timer it;
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/*
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* Only FIFO tasks can disable the tick since they don't need the forced
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* preemption.
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*/
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WARN_ON_ONCE(current->policy != SCHED_FIFO);
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WARN_ON_ONCE(current->nr_cpus_allowed != 1);
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WARN_ON_ONCE(!(current->flags & PF_KTHREAD));
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WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY));
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WARN_ON_ONCE(!duration_us);
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rcu_sleep_check();
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preempt_disable();
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current->flags |= PF_IDLE;
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cpuidle_use_deepest_state(true);
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it.done = 0;
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hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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it.timer.function = idle_inject_timer_fn;
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hrtimer_start(&it.timer, ns_to_ktime(duration_us * NSEC_PER_USEC),
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HRTIMER_MODE_REL_PINNED);
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while (!READ_ONCE(it.done))
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do_idle();
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cpuidle_use_deepest_state(false);
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current->flags &= ~PF_IDLE;
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preempt_fold_need_resched();
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preempt_enable();
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}
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EXPORT_SYMBOL_GPL(play_idle);
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void cpu_startup_entry(enum cpuhp_state state)
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{
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arch_cpu_idle_prepare();
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cpuhp_online_idle(state);
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while (1)
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do_idle();
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}
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/*
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* idle-task scheduling class.
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*/
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#ifdef CONFIG_SMP
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static int
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select_task_rq_idle(struct task_struct *p, int cpu, int sd_flag, int flags)
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{
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return task_cpu(p); /* IDLE tasks as never migrated */
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}
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#endif
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/*
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* Idle tasks are unconditionally rescheduled:
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*/
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static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
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{
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resched_curr(rq);
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}
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static void put_prev_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
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{
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}
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static void set_next_task_idle(struct rq *rq, struct task_struct *next)
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{
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update_idle_core(rq);
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schedstat_inc(rq->sched_goidle);
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}
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static struct task_struct *
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pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
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{
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struct task_struct *next = rq->idle;
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if (prev)
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put_prev_task(rq, prev);
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set_next_task_idle(rq, next);
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return next;
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}
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/*
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* It is not legal to sleep in the idle task - print a warning
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* message if some code attempts to do it:
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*/
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static void
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dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
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{
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raw_spin_unlock_irq(&rq->lock);
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printk(KERN_ERR "bad: scheduling from the idle thread!\n");
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dump_stack();
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raw_spin_lock_irq(&rq->lock);
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}
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/*
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* scheduler tick hitting a task of our scheduling class.
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*
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* NOTE: This function can be called remotely by the tick offload that
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* goes along full dynticks. Therefore no local assumption can be made
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* and everything must be accessed through the @rq and @curr passed in
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* parameters.
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*/
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static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
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{
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}
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static void switched_to_idle(struct rq *rq, struct task_struct *p)
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{
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BUG();
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}
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static void
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prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
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{
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BUG();
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}
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static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
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{
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return 0;
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}
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static void update_curr_idle(struct rq *rq)
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{
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}
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/*
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* Simple, special scheduling class for the per-CPU idle tasks:
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*/
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const struct sched_class idle_sched_class = {
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/* .next is NULL */
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/* no enqueue/yield_task for idle tasks */
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/* dequeue is not valid, we print a debug message there: */
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.dequeue_task = dequeue_task_idle,
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.check_preempt_curr = check_preempt_curr_idle,
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.pick_next_task = pick_next_task_idle,
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.put_prev_task = put_prev_task_idle,
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.set_next_task = set_next_task_idle,
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#ifdef CONFIG_SMP
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.select_task_rq = select_task_rq_idle,
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.set_cpus_allowed = set_cpus_allowed_common,
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#endif
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.task_tick = task_tick_idle,
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.get_rr_interval = get_rr_interval_idle,
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.prio_changed = prio_changed_idle,
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.switched_to = switched_to_idle,
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.update_curr = update_curr_idle,
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};
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