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3WhCfnrZpok5PbtSNQUQ5Tovovi10GWvxJug9d8aDFT2wPj1YU96GfEM/q2jQ0eqF0xK6ke8Kjn 1nRANxUdbD9sulseSxoUcPYWqP2UMjo5mlJM0sP2naR8STFtznok6vNyDDT1DwM6Xpufq7audIW kqrne53ow1wMEPt+906AZglu/qAqpukimY/yB1mEcus551zPkMVvVja9A6ElpN2pUmk21siAsME UQdczkV7fePnXqNz3ZpXDlp1xEx71uy+DZfXdYupvGvbLjm1/64X+KcITHr3ku7UzsiRz8Sx1u1 wdjWSwv2IlnrdpH+pJy28TzLDGWxWBxCUtsJN/aaHohD5jcerKBeVQCWOoJskN2IgVO0PLcA X-Authority-Analysis: v=2.4 cv=D6hHKuRj c=1 sm=1 tr=0 ts=68655de0 b=1 cx=c_pps a=zPCbziy225d3KhSqZt3L1A==:117 a=zPCbziy225d3KhSqZt3L1A==:17 a=6eWqkTHjU83fiwn7nKZWdM+Sl24=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=wKuvFiaSGQ0qltdbU6+NXLB8nM8=:19 a=Ol13hO9ccFRV9qXi2t6ftBPywas=:19 a=xqWC_Br6kY4A:10 a=IkcTkHD0fZMA:10 a=Wb1JkmetP80A:10 a=GoEa3M9JfhUA:10 a=968KyxNXAAAA:8 a=E2GMToCHSwIVQm4d3g4A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 cc=ntf awl=host:13215 X-Proofpoint-ORIG-GUID: 52oQaA1fIn-FIiQ-QvEBPKF1btFX84cu On Wed, Jul 02, 2025 at 08:23:58PM +0800, Liangyan wrote: > We test that unixbench spawn has big improvement in Intel 8582c 120-CPU > guest vm if switch to qspinlock. And ARM or AMD? > > Command: ./Run -c 120 spawn > > Use virt_spin_lock: > System Benchmarks Partial Index BASELINE RESULT INDEX > Process Creation 126.0 71878.4 5704.6 > ======== > System Benchmarks Index Score (Partial Only) 5704.6 > > > Use qspinlock: > System Benchmarks Partial Index BASELINE RESULT INDEX > Process Creation 126.0 173566.6 13775.1 > ======== > System Benchmarks Index Score (Partial Only 13775.1 > > > Regards, > Liangyan > > On 2025/7/2 16:19, Bibo Mao wrote: > > > > > > On 2025/7/2 下午2:42, Liangyan wrote: > > > When KVM_HINTS_REALTIME is set and KVM_FEATURE_PV_UNHALT is clear, > > > currently guest will use virt_spin_lock. > > > Since KVM_HINTS_REALTIME is set, use native qspinlock should be safe > > > and have better performance than virt_spin_lock. > > Just be curious, do you have actual data where native qspinlock has > > better performance than virt_spin_lock()? > > > > By my understanding, qspinlock is not friendly with VM. When lock is > > released, it is acquired with one by one order in contending queue. If > > the first vCPU in contending queue is preempted, the other vCPUs can not > > get lock. On physical machine it is almost impossible that CPU > > contending lock is preempted. > > > > Regards > > Bibo Mao > > > > > > Signed-off-by: Liangyan > > > --- > > >   arch/x86/kernel/kvm.c | 18 +++++++++--------- > > >   1 file changed, 9 insertions(+), 9 deletions(-) > > > > > > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > > > index 921c1c783bc1..9080544a4007 100644 > > > --- a/arch/x86/kernel/kvm.c > > > +++ b/arch/x86/kernel/kvm.c > > > @@ -1072,6 +1072,15 @@ static void kvm_wait(u8 *ptr, u8 val) > > >    */ > > >   void __init kvm_spinlock_init(void) > > >   { > > > +    /* > > > +     * Disable PV spinlocks and use native qspinlock when dedicated > > > pCPUs > > > +     * are available. > > > +     */ > > > +    if (kvm_para_has_hint(KVM_HINTS_REALTIME)) { > > > +        pr_info("PV spinlocks disabled with KVM_HINTS_REALTIME > > > hints\n"); > > > +        goto out; > > > +    } > > > + > > >       /* > > >        * In case host doesn't support KVM_FEATURE_PV_UNHALT there is > > > still an > > >        * advantage of keeping virt_spin_lock_key enabled: > > > virt_spin_lock() is > > > @@ -1082,15 +1091,6 @@ void __init kvm_spinlock_init(void) > > >           return; > > >       } > > > -    /* > > > -     * Disable PV spinlocks and use native qspinlock when dedicated > > > pCPUs > > > -     * are available. > > > -     */ > > > -    if (kvm_para_has_hint(KVM_HINTS_REALTIME)) { > > > -        pr_info("PV spinlocks disabled with KVM_HINTS_REALTIME > > > hints\n"); > > > -        goto out; > > > -    } > > > - > > >       if (num_possible_cpus() == 1) { > > >           pr_info("PV spinlocks disabled, single CPU\n"); > > >           goto out; > > > > > > >