diff options
| author | Venki Pallipadi <venkatesh.pallipadi@intel.com> | 2008-01-30 13:32:01 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-01-30 13:32:01 +0100 |
| commit | bde6f5f59c2b2b48a7a849c129d5b48838fe77ee (patch) | |
| tree | 4fa3befdfa227db56770a0dc85b8fc18be232f70 /arch | |
| parent | 7d409d6057c7244f8757ce15245f6df27271be0c (diff) | |
x86: voluntary leave_mm before entering ACPI C3
Aviod TLB flush IPIs during C3 states by voluntary leave_mm()
before entering C3.
The performance impact of TLB flush on C3 should not be significant with
respect to C3 wakeup latency. Also, CPUs tend to flush TLB in hardware while in
C3 anyways.
On a 8 logical CPU system, running make -j2, the number of tlbflush IPIs goes
down from 40 per second to ~ 0. Total number of interrupts during the run
of this workload was ~1200 per second, which makes it ~3% savings in wakeups.
There was no measurable performance or power impact however.
[ akpm@linux-foundation.org: symbol export fixes. ]
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/smp_32.c | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/smp_64.c | 3 |
2 files changed, 4 insertions, 2 deletions
diff --git a/arch/x86/kernel/smp_32.c b/arch/x86/kernel/smp_32.c index 070816ac79e..dc0cde9d16f 100644 --- a/arch/x86/kernel/smp_32.c +++ b/arch/x86/kernel/smp_32.c @@ -256,13 +256,14 @@ static DEFINE_SPINLOCK(tlbstate_lock); * We need to reload %cr3 since the page tables may be going * away from under us.. */ -void leave_mm(unsigned long cpu) +void leave_mm(int cpu) { if (per_cpu(cpu_tlbstate, cpu).state == TLBSTATE_OK) BUG(); cpu_clear(cpu, per_cpu(cpu_tlbstate, cpu).active_mm->cpu_vm_mask); load_cr3(swapper_pg_dir); } +EXPORT_SYMBOL_GPL(leave_mm); /* * diff --git a/arch/x86/kernel/smp_64.c b/arch/x86/kernel/smp_64.c index 02a6533e890..2fd74b06db6 100644 --- a/arch/x86/kernel/smp_64.c +++ b/arch/x86/kernel/smp_64.c @@ -69,13 +69,14 @@ static DEFINE_PER_CPU(union smp_flush_state, flush_state); * We cannot call mmdrop() because we are in interrupt context, * instead update mm->cpu_vm_mask. */ -static inline void leave_mm(int cpu) +void leave_mm(int cpu) { if (read_pda(mmu_state) == TLBSTATE_OK) BUG(); cpu_clear(cpu, read_pda(active_mm)->cpu_vm_mask); load_cr3(swapper_pg_dir); } +EXPORT_SYMBOL_GPL(leave_mm); /* * |