During some profiling I noticed that default_idle causes a lot of
memory traffic. I think that is caused by the atomic operations
to clear/set the polling flag in thread_info. There is actually
no reason to make this atomic - only the idle thread does it
to itself, other CPUs only read it. So I moved it into ti->status.
Converted i386/x86-64/ia64 for now because that was the easiest
way to fix ACPI which also manipulates these flags in its idle
function.
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Andi Kleen <[email protected]>
---
arch/i386/kernel/apm.c | 6 +++---
arch/i386/kernel/process.c | 6 +++---
arch/ia64/kernel/process.c | 4 ++--
arch/x86_64/kernel/process.c | 7 +++----
drivers/acpi/processor_idle.c | 12 ++++++------
include/asm-i386/thread_info.h | 7 ++++---
include/asm-ia64/thread_info.h | 5 +++++
include/asm-x86_64/thread_info.h | 6 ++++--
kernel/sched.c | 9 +++++++--
9 files changed, 37 insertions(+), 25 deletions(-)
Index: linux/arch/x86_64/kernel/process.c
===================================================================
--- linux.orig/arch/x86_64/kernel/process.c
+++ linux/arch/x86_64/kernel/process.c
@@ -110,7 +110,7 @@ static void default_idle(void)
{
local_irq_enable();
- clear_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status &= ~TS_POLLING;
smp_mb__after_clear_bit();
while (!need_resched()) {
local_irq_disable();
@@ -119,7 +119,7 @@ static void default_idle(void)
else
local_irq_enable();
}
- set_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status |= TS_POLLING;
}
/*
@@ -202,8 +202,7 @@ static inline void play_dead(void)
*/
void cpu_idle (void)
{
- set_thread_flag(TIF_POLLING_NRFLAG);
-
+ current_thread_info()->status |= TS_POLLING;
/* endless idle loop with no priority at all */
while (1) {
while (!need_resched()) {
Index: linux/drivers/acpi/processor_idle.c
===================================================================
--- linux.orig/drivers/acpi/processor_idle.c
+++ linux/drivers/acpi/processor_idle.c
@@ -206,11 +206,11 @@ acpi_processor_power_activate(struct acp
static void acpi_safe_halt(void)
{
- clear_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status &= ~TS_POLLING;
smp_mb__after_clear_bit();
if (!need_resched())
safe_halt();
- set_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status |= TS_POLLING;
}
static atomic_t c3_cpu_count;
@@ -330,10 +330,10 @@ static void acpi_processor_idle(void)
* Invoke the current Cx state to put the processor to sleep.
*/
if (cx->type == ACPI_STATE_C2 || cx->type == ACPI_STATE_C3) {
- clear_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status &= ~TS_POLLING;
smp_mb__after_clear_bit();
if (need_resched()) {
- set_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status |= TS_POLLING;
local_irq_enable();
return;
}
@@ -371,7 +371,7 @@ static void acpi_processor_idle(void)
t2 = inl(acpi_fadt.xpm_tmr_blk.address);
/* Re-enable interrupts */
local_irq_enable();
- set_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status |= TS_POLLING;
/* Compute time (ticks) that we were actually asleep */
sleep_ticks =
ticks_elapsed(t1, t2) - cx->latency_ticks - C2_OVERHEAD;
@@ -411,7 +411,7 @@ static void acpi_processor_idle(void)
/* Re-enable interrupts */
local_irq_enable();
- set_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status |= TS_POLLING;
/* Compute time (ticks) that we were actually asleep */
sleep_ticks =
ticks_elapsed(t1, t2) - cx->latency_ticks - C3_OVERHEAD;
Index: linux/include/asm-i386/thread_info.h
===================================================================
--- linux.orig/include/asm-i386/thread_info.h
+++ linux/include/asm-i386/thread_info.h
@@ -140,8 +140,7 @@ register unsigned long current_stack_poi
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
#define TIF_SECCOMP 8 /* secure computing */
#define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal() */
-#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
-#define TIF_MEMDIE 17
+#define TIF_MEMDIE 16
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
@@ -153,7 +152,6 @@ register unsigned long current_stack_poi
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
-#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
/* work to do on interrupt/exception return */
#define _TIF_WORK_MASK \
@@ -170,6 +168,9 @@ register unsigned long current_stack_poi
* have to worry about atomic accesses.
*/
#define TS_USEDFPU 0x0001 /* FPU was used by this task this quantum (SMP) */
+#define TS_POLLING 0x0002 /* True if in idle loop and not sleeping */
+
+#define tsk_is_polling(t) ((t)->thread_info->status & TS_POLLING)
#endif /* __KERNEL__ */
Index: linux/include/asm-ia64/thread_info.h
===================================================================
--- linux.orig/include/asm-ia64/thread_info.h
+++ linux/include/asm-ia64/thread_info.h
@@ -27,6 +27,7 @@ struct thread_info {
__u32 flags; /* thread_info flags (see TIF_*) */
__u32 cpu; /* current CPU */
__u32 last_cpu; /* Last CPU thread ran on */
+ __u32 status; /* Thread synchronous flags */
mm_segment_t addr_limit; /* user-level address space limit */
int preempt_count; /* 0=premptable, <0=BUG; will also serve as bh-counter */
struct restart_block restart_block;
@@ -103,4 +104,8 @@ struct thread_info {
/* like TIF_ALLWORK_BITS but sans TIF_SYSCALL_TRACE or TIF_SYSCALL_AUDIT */
#define TIF_WORK_MASK (TIF_ALLWORK_MASK&~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT))
+#define TS_POLLING 1 /* true if in idle loop and not sleeping */
+
+#define tsk_is_polling(t) ((t)->thread_info->status & TS_POLLING)
+
#endif /* _ASM_IA64_THREAD_INFO_H */
Index: linux/include/asm-x86_64/thread_info.h
===================================================================
--- linux.orig/include/asm-x86_64/thread_info.h
+++ linux/include/asm-x86_64/thread_info.h
@@ -101,7 +101,7 @@ static inline struct thread_info *stack_
#define TIF_IRET 5 /* force IRET */
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
#define TIF_SECCOMP 8 /* secure computing */
-#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
+/* 16 free */
#define TIF_IA32 17 /* 32bit process */
#define TIF_FORK 18 /* ret_from_fork */
#define TIF_ABI_PENDING 19
@@ -115,7 +115,6 @@ static inline struct thread_info *stack_
#define _TIF_IRET (1<<TIF_IRET)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
-#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_IA32 (1<<TIF_IA32)
#define _TIF_FORK (1<<TIF_FORK)
#define _TIF_ABI_PENDING (1<<TIF_ABI_PENDING)
@@ -137,6 +136,9 @@ static inline struct thread_info *stack_
*/
#define TS_USEDFPU 0x0001 /* FPU was used by this task this quantum (SMP) */
#define TS_COMPAT 0x0002 /* 32bit syscall active */
+#define TS_POLLING 0x0004 /* true if in idle loop and not sleeping */
+
+#define tsk_is_polling(t) ((t)->thread_info->status & TS_POLLING)
#endif /* __KERNEL__ */
Index: linux/kernel/sched.c
===================================================================
--- linux.orig/kernel/sched.c
+++ linux/kernel/sched.c
@@ -818,6 +818,11 @@ static void deactivate_task(struct task_
* the target CPU.
*/
#ifdef CONFIG_SMP
+
+#ifndef tsk_is_polling
+#define tsk_is_polling(t) test_tsk_thread_flag(t, TIF_POLLING_NRFLAG)
+#endif
+
static void resched_task(task_t *p)
{
int cpu;
@@ -833,9 +838,9 @@ static void resched_task(task_t *p)
if (cpu == smp_processor_id())
return;
- /* NEED_RESCHED must be visible before we test POLLING_NRFLAG */
+ /* NEED_RESCHED must be visible before we test polling */
smp_mb();
- if (!test_tsk_thread_flag(p, TIF_POLLING_NRFLAG))
+ if (!tsk_is_polling(p))
smp_send_reschedule(cpu);
}
#else
Index: linux/arch/i386/kernel/process.c
===================================================================
--- linux.orig/arch/i386/kernel/process.c
+++ linux/arch/i386/kernel/process.c
@@ -102,7 +102,7 @@ void default_idle(void)
local_irq_enable();
if (!hlt_counter && boot_cpu_data.hlt_works_ok) {
- clear_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status &= ~TS_POLLING;
smp_mb__after_clear_bit();
while (!need_resched()) {
local_irq_disable();
@@ -111,7 +111,7 @@ void default_idle(void)
else
local_irq_enable();
}
- set_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status |= TS_POLLING;
} else {
while (!need_resched())
cpu_relax();
@@ -174,7 +174,7 @@ void cpu_idle(void)
{
int cpu = smp_processor_id();
- set_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status |= TS_POLLING;
/* endless idle loop with no priority at all */
while (1) {
Index: linux/arch/ia64/kernel/process.c
===================================================================
--- linux.orig/arch/ia64/kernel/process.c
+++ linux/arch/ia64/kernel/process.c
@@ -272,9 +272,9 @@ cpu_idle (void)
/* endless idle loop with no priority at all */
while (1) {
if (can_do_pal_halt)
- clear_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status &= ~TS_POLLING;
else
- set_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status |= TS_POLLING;
if (!need_resched()) {
void (*idle)(void);
Index: linux/arch/i386/kernel/apm.c
===================================================================
--- linux.orig/arch/i386/kernel/apm.c
+++ linux/arch/i386/kernel/apm.c
@@ -764,9 +764,9 @@ static int apm_do_idle(void)
int idled = 0;
int polling;
- polling = test_thread_flag(TIF_POLLING_NRFLAG);
+ polling = !!(current_thread_info()->status & TS_POLLING);
if (polling) {
- clear_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status &= ~TS_POLLING;
smp_mb__after_clear_bit();
}
if (!need_resched()) {
@@ -774,7 +774,7 @@ static int apm_do_idle(void)
ret = apm_bios_call_simple(APM_FUNC_IDLE, 0, 0, &eax);
}
if (polling)
- set_thread_flag(TIF_POLLING_NRFLAG);
+ current_thread_info()->status |= TS_POLLING;
if (!idled)
return 0;
-
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