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perf counters: protect them against CSTATE transitions

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Impact: fix rare lost events problem

There are CPUs whose performance counters misbehave on CSTATE transitions,
so provide a way to just disable/enable them around deep idle methods.

(hw_perf_enable_all() is cheap on x86.)

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Thomas Gleixner 2008-12-09 21:43:39 +01:00 committed by Ingo Molnar
parent 43874d238d
commit 4ac13294e4
3 changed files with 26 additions and 2 deletions
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16
arch/x86/kernel/cpu/perf_counter.c
View File

@ -12,6 +12,7 @@
#include <linux/notifier.h>
#include <linux/hardirq.h>
#include <linux/kprobes.h>
#include <linux/module.h>
#include <linux/kdebug.h>
#include <linux/sched.h>
@ -119,10 +120,21 @@ void hw_perf_enable_all(void)
wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, perf_counter_mask, 0);
}
void hw_perf_disable_all(void)
void hw_perf_restore_ctrl(u64 ctrl)
{
wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, 0, 0);
wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, ctrl, 0);
}
EXPORT_SYMBOL_GPL(hw_perf_restore_ctrl);
u64 hw_perf_disable_all(void)
{
u64 ctrl;
rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, ctrl);
wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, 0, 0);
return ctrl;
}
EXPORT_SYMBOL_GPL(hw_perf_disable_all);
static inline void
__hw_perf_counter_disable(struct hw_perf_counter *hwc, unsigned int idx)

8
drivers/acpi/processor_idle.c
View File

@ -270,8 +270,11 @@ static atomic_t c3_cpu_count;
/* Common C-state entry for C2, C3, .. */
static void acpi_cstate_enter(struct acpi_processor_cx *cstate)
{
u64 pctrl;
/* Don't trace irqs off for idle */
stop_critical_timings();
pctrl = hw_perf_disable_all();
if (cstate->entry_method == ACPI_CSTATE_FFH) {
/* Call into architectural FFH based C-state */
acpi_processor_ffh_cstate_enter(cstate);
@ -284,6 +287,7 @@ static void acpi_cstate_enter(struct acpi_processor_cx *cstate)
gets asserted in time to freeze execution properly. */
unused = inl(acpi_gbl_FADT.xpm_timer_block.address);
}
hw_perf_restore_ctrl(pctrl);
start_critical_timings();
}
#endif /* !CONFIG_CPU_IDLE */
@ -1425,8 +1429,11 @@ static inline void acpi_idle_update_bm_rld(struct acpi_processor *pr,
*/
static inline void acpi_idle_do_entry(struct acpi_processor_cx *cx)
{
u64 pctrl;
/* Don't trace irqs off for idle */
stop_critical_timings();
pctrl = hw_perf_disable_all();
if (cx->entry_method == ACPI_CSTATE_FFH) {
/* Call into architectural FFH based C-state */
acpi_processor_ffh_cstate_enter(cx);
@ -1441,6 +1448,7 @@ static inline void acpi_idle_do_entry(struct acpi_processor_cx *cx)
gets asserted in time to freeze execution properly. */
unused = inl(acpi_gbl_FADT.xpm_timer_block.address);
}
hw_perf_restore_ctrl(pctrl);
start_critical_timings();
}

4
include/linux/perf_counter.h
View File

@ -156,6 +156,8 @@ extern void perf_counter_task_tick(struct task_struct *task, int cpu);
extern void perf_counter_init_task(struct task_struct *task);
extern void perf_counter_notify(struct pt_regs *regs);
extern void perf_counter_print_debug(void);
extern void hw_perf_restore_ctrl(u64 ctrl);
extern u64 hw_perf_disable_all(void);
#else
static inline void
perf_counter_task_sched_in(struct task_struct *task, int cpu) { }
@ -166,6 +168,8 @@ perf_counter_task_tick(struct task_struct *task, int cpu) { }
static inline void perf_counter_init_task(struct task_struct *task) { }
static inline void perf_counter_notify(struct pt_regs *regs) { }
static inline void perf_counter_print_debug(void) { }
static inline void hw_perf_restore_ctrl(u64 ctrl) { }
static inline u64 hw_perf_disable_all(void) { return 0; }
#endif
#endif /* _LINUX_PERF_COUNTER_H */