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c43dce6f13
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>
64 lines
1.5 KiB
C
64 lines
1.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_LOONGARCH_QSPINLOCK_H
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#define _ASM_LOONGARCH_QSPINLOCK_H
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#include <asm/kvm_para.h>
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#include <linux/jump_label.h>
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#ifdef CONFIG_PARAVIRT
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DECLARE_STATIC_KEY_FALSE(virt_preempt_key);
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DECLARE_STATIC_KEY_FALSE(virt_spin_lock_key);
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DECLARE_PER_CPU(struct kvm_steal_time, steal_time);
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#define virt_spin_lock virt_spin_lock
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static inline bool virt_spin_lock(struct qspinlock *lock)
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{
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int val;
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if (!static_branch_unlikely(&virt_spin_lock_key))
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return false;
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/*
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* On hypervisors without PARAVIRT_SPINLOCKS support we fall
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* back to a Test-and-Set spinlock, because fair locks have
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* horrible lock 'holder' preemption issues.
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*/
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__retry:
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val = atomic_read(&lock->val);
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if (val || !atomic_try_cmpxchg(&lock->val, &val, _Q_LOCKED_VAL)) {
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cpu_relax();
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goto __retry;
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}
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return true;
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}
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/*
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* Macro is better than inline function here
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* With macro, parameter cpu is parsed only when it is used.
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* With inline function, parameter cpu is parsed even though it is not used.
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* This may cause cache line thrashing across NUMA nodes.
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*/
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#define vcpu_is_preempted(cpu) \
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({ \
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bool __val; \
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\
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if (!static_branch_unlikely(&virt_preempt_key)) \
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__val = false; \
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else { \
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struct kvm_steal_time *src; \
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src = &per_cpu(steal_time, cpu); \
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__val = !!(READ_ONCE(src->preempted) & KVM_VCPU_PREEMPTED); \
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} \
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__val; \
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})
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#endif /* CONFIG_PARAVIRT */
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#include <asm-generic/qspinlock.h>
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#endif // _ASM_LOONGARCH_QSPINLOCK_H
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