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From:   johnnyaiai <arafatms@outlook.com>
To:     jgross@suse.com
Cc:     tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        dave.hansen@linux.intel.com, hpa@zytor.com,
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        johnnyaiai <johnnyaiai@tencent.com>
Subject: [PATCH] locking/paravirt: Fix performance regression on core bonded vCPU
Date:   Thu,  3 Nov 2022 20:13:19 +0800
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From: johnnyaiai <johnnyaiai@tencent.com>

virt_spin_lock() is preferred over native qspinlock when
vCPU is preempted. But brings a lot of regression while
vCPU is not preempted. Provide a early param 'novirtlock'
to choose would be better.

will-it-scale/lock2_threads -s 10 -t 64
baseline    afterpatch
559938       2166135

Signed-off-by: johnnyaiai <johnnyaiai@tencent.com>
---
 arch/x86/kernel/paravirt.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 59d3d2763..529cf23fe 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -107,6 +107,13 @@ static unsigned paravirt_patch_jmp(void *insn_buff, const void *target,
 
 DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key);
 
+static __init int parse_novirtspin(char *arg)
+{
+	static_branch_disable(&virt_spin_lock_key);
+	return 0;
+}
+early_param("novirtspin", parse_novirtspin);
+
 void __init native_pv_lock_init(void)
 {
 	if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
-- 
2.27.0