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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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ad65782fba
Optimize user and exception entry/exit APIs with static keys. This minimize the overhead for those who enable CONFIG_NO_HZ_FULL without always using it. Having no range passed to nohz_full= should result in the probes to be nopped (at least we hope so...). If this proves not be enough in the long term, we'll need to bring an exception slow path by re-routing the exception handlers. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Kevin Hilman <khilman@linaro.org>
121 lines
2.9 KiB
C
121 lines
2.9 KiB
C
#ifndef _LINUX_CONTEXT_TRACKING_H
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#define _LINUX_CONTEXT_TRACKING_H
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#include <linux/sched.h>
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#include <linux/percpu.h>
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#include <linux/vtime.h>
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#include <linux/static_key.h>
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#include <asm/ptrace.h>
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struct context_tracking {
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/*
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* When active is false, probes are unset in order
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* to minimize overhead: TIF flags are cleared
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* and calls to user_enter/exit are ignored. This
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* may be further optimized using static keys.
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*/
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bool active;
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enum ctx_state {
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IN_KERNEL = 0,
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IN_USER,
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} state;
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};
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#ifdef CONFIG_CONTEXT_TRACKING
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extern struct static_key context_tracking_enabled;
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DECLARE_PER_CPU(struct context_tracking, context_tracking);
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static inline bool context_tracking_in_user(void)
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{
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return __this_cpu_read(context_tracking.state) == IN_USER;
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}
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static inline bool context_tracking_active(void)
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{
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return __this_cpu_read(context_tracking.active);
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}
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extern void context_tracking_cpu_set(int cpu);
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extern void context_tracking_user_enter(void);
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extern void context_tracking_user_exit(void);
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static inline void user_enter(void)
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{
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if (static_key_false(&context_tracking_enabled))
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context_tracking_user_enter();
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}
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static inline void user_exit(void)
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{
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if (static_key_false(&context_tracking_enabled))
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context_tracking_user_exit();
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}
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static inline enum ctx_state exception_enter(void)
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{
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enum ctx_state prev_ctx;
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if (!static_key_false(&context_tracking_enabled))
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return 0;
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prev_ctx = this_cpu_read(context_tracking.state);
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context_tracking_user_exit();
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return prev_ctx;
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}
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static inline void exception_exit(enum ctx_state prev_ctx)
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{
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if (static_key_false(&context_tracking_enabled)) {
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if (prev_ctx == IN_USER)
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context_tracking_user_enter();
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}
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}
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extern void context_tracking_task_switch(struct task_struct *prev,
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struct task_struct *next);
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#else
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static inline bool context_tracking_in_user(void) { return false; }
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static inline void user_enter(void) { }
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static inline void user_exit(void) { }
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static inline enum ctx_state exception_enter(void) { return 0; }
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static inline void exception_exit(enum ctx_state prev_ctx) { }
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static inline void context_tracking_task_switch(struct task_struct *prev,
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struct task_struct *next) { }
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#endif /* !CONFIG_CONTEXT_TRACKING */
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#ifdef CONFIG_CONTEXT_TRACKING_FORCE
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extern void context_tracking_init(void);
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#else
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static inline void context_tracking_init(void) { }
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#endif /* CONFIG_CONTEXT_TRACKING_FORCE */
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
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extern void guest_enter(void);
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extern void guest_exit(void);
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#else
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static inline void guest_enter(void)
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{
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/*
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* This is running in ioctl context so its safe
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* to assume that it's the stime pending cputime
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* to flush.
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*/
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vtime_account_system(current);
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current->flags |= PF_VCPU;
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}
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static inline void guest_exit(void)
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{
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/* Flush the guest cputime we spent on the guest */
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vtime_account_system(current);
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current->flags &= ~PF_VCPU;
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}
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#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */
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#endif
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