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LoongArch: KVM: Make vcpu_is_preempted() as a macro rather than function

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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: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Bibo Mao 2026-04-09 18:56:36 +08:00 committed by Huacai Chen
parent aac656857e
commit c43dce6f13
2 changed files with 24 additions and 18 deletions
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26
arch/loongarch/include/asm/qspinlock.h
View File

@ -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 */

16
arch/loongarch/kernel/paravirt.c
View File

@ -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)