linux-kernel - [PATCH] locking/paravirt: Fix performance regression on core bonded vCPU

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Date:   Thu,  3 Nov 2022 20:10:06 +0800
From:   johnnyaiai <arafatms@...look.com>
To:     jgross@...e.com
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        johnnyaiai <johnnyaiai@...cent.com>
Subject: [PATCH] locking/paravirt: Fix performance regression on core bonded vCPU

From: johnnyaiai <johnnyaiai@...cent.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@...cent.com>
---
 kernel/locking/qspinlock.c | 3 ---
 1 file changed, 3 deletions(-)

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