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git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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e5ba90abb2
Similar with x86, when VM is detected, revert to a simple test-and-set
lock to avoid the horrors of queue preemption.
Tested on 3C5000 Dual-way machine with 32 cores and 2 numa nodes,
test case is kcbench on kernel mainline 6.10, the detailed command is
"kcbench --src /root/src/linux"
Performance on host machine
kernel compile time performance impact
Original 150.29 seconds
With patch 150.19 seconds almost no impact
Performance on virtual machine:
1. 1 VM with 32 vCPUs and 2 numa node, numa node pinned
kernel compile time performance impact
Original 170.87 seconds
With patch 171.73 seconds almost no impact
2. 2 VMs, each VM with 32 vCPUs and 2 numa node, numa node pinned
kernel compile time performance impact
Original 2362.04 seconds
With patch 354.73 seconds +565%
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
41 lines
834 B
C
41 lines
834 B
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 <linux/jump_label.h>
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#ifdef CONFIG_PARAVIRT
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DECLARE_STATIC_KEY_FALSE(virt_spin_lock_key);
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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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#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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