Commit c43dce6f authored by Bibo Mao's avatar Bibo Mao Committed by Huacai Chen
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LoongArch: KVM: Make vcpu_is_preempted() as a macro rather than function 



vcpu_is_preempted() is performance sensitive that called in function
osq_lock(), here make it as a macro. So that parameter is not parsed
at most time, it can avoid cache line thrashing across numa nodes.

Here is part of UnixBench result on Loongson-3C5000 DualWay machine with
32 cores and 2 numa nodes.

          original    inline   macro
execl     7025.7      6991.2   7242.3
fstime    474.6       703.1    1071

From the test result, making vcpu_is_preempted() as a macro is the best,
and there is some improvment compared with the original function method.

Signed-off-by: default avatarBibo Mao <maobibo@loongson.cn>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent aac65685

arch/loongarch/include/asm/qspinlock.h

+22 −4
Original line number Diff line number Diff line
@@ -2,11 +2,13 @@ 
#ifndef _ASM_LOONGARCH_QSPINLOCK_H

#define _ASM_LOONGARCH_QSPINLOCK_H



#include <asm/kvm_para.h>

#include <linux/jump_label.h>



#ifdef CONFIG_PARAVIRT



DECLARE_STATIC_KEY_FALSE(virt_preempt_key);

DECLARE_STATIC_KEY_FALSE(virt_spin_lock_key);

DECLARE_PER_CPU(struct kvm_steal_time, steal_time);



#define virt_spin_lock virt_spin_lock
@@ -34,9 +36,25 @@ static inline bool virt_spin_lock(struct qspinlock *lock) 
	return true;

}



#define vcpu_is_preempted vcpu_is_preempted



bool vcpu_is_preempted(int cpu);

/*

 * Macro is better than inline function here

 * With macro, parameter cpu is parsed only when it is used.

 * With inline function, parameter cpu is parsed even though it is not used.

 * This may cause cache line thrashing across NUMA nodes.

 */

#define vcpu_is_preempted(cpu)							\

({										\

	bool __val;								\

										\

	if (!static_branch_unlikely(&virt_preempt_key))				\

		__val = false;							\

	else {									\

		struct kvm_steal_time *src;					\

		src = &per_cpu(steal_time, cpu);				\

		__val = !!(READ_ONCE(src->preempted) & KVM_VCPU_PREEMPTED);	\

	}									\

	__val;									\

})



#endif /* CONFIG_PARAVIRT */

arch/loongarch/kernel/paravirt.c

+2 −14
Original line number Diff line number Diff line
@@ -10,9 +10,9 @@ 
#include <asm/paravirt.h>



static int has_steal_clock;

static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);

static DEFINE_STATIC_KEY_FALSE(virt_preempt_key);

DEFINE_STATIC_KEY_FALSE(virt_preempt_key);

DEFINE_STATIC_KEY_FALSE(virt_spin_lock_key);

DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);



static bool steal_acc = true;
@@ -260,18 +260,6 @@ static int pv_time_cpu_down_prepare(unsigned int cpu) 


	return 0;

}



bool vcpu_is_preempted(int cpu)

{

	struct kvm_steal_time *src;



	if (!static_branch_unlikely(&virt_preempt_key))

		return false;



	src = &per_cpu(steal_time, cpu);

	return !!(src->preempted & KVM_VCPU_PREEMPTED);

}

EXPORT_SYMBOL(vcpu_is_preempted);

#endif



static void pv_cpu_reboot(void *unused)