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Date: Wed, 7 May 2014 15:07:06 -0400
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: Waiman Long <Waiman.Long@...com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>,
linux-arch@...r.kernel.org, x86@...nel.org,
linux-kernel@...r.kernel.org,
virtualization@...ts.linux-foundation.org,
xen-devel@...ts.xenproject.org, kvm@...r.kernel.org,
Paolo Bonzini <paolo.bonzini@...il.com>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Rik van Riel <riel@...hat.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
David Vrabel <david.vrabel@...rix.com>,
Oleg Nesterov <oleg@...hat.com>,
Gleb Natapov <gleb@...hat.com>,
Scott J Norton <scott.norton@...com>,
Chegu Vinod <chegu_vinod@...com>
Subject: Re: [PATCH v10 18/19] pvqspinlock, x86: Enable PV qspinlock PV for
KVM
> Raghavendra KT had done some performance testing on this patch with
> the following results:
>
> Overall we are seeing good improvement for pv-unfair version.
>
> System: 32 cpu sandybridge with HT on (4 node with 32 GB each)
> Guest : 8GB with 16 vcpu/VM.
> Average was taken over 8-10 data points.
>
> Base = 3.15-rc2 with PRAVIRT_SPINLOCK = y
>
> A = 3.15-rc2 + qspinlock v9 patch with QUEUE_SPINLOCK = y
> PRAVIRT_SPINLOCK = y PARAVIRT_UNFAIR_LOCKS = y (unfair lock)
>
> B = 3.15-rc2 + qspinlock v9 patch with QUEUE_SPINLOCK = y
> PRAVIRT_SPINLOCK = n PARAVIRT_UNFAIR_LOCKS = n
> (queue spinlock without paravirt)
>
> C = 3.15-rc2 + qspinlock v9 patch with QUEUE_SPINLOCK = y
> PRAVIRT_SPINLOCK = y PARAVIRT_UNFAIR_LOCKS = n
> (queue spinlock with paravirt)
Could you do s/PRAVIRT/PARAVIRT/ please?
>
> Ebizzy %improvements
> ====================
> overcommit A B C
> 0.5x 4.4265 2.0611 1.5824
> 1.0x 0.9015 -7.7828 4.5443
> 1.5x 46.1162 -2.9845 -3.5046
> 2.0x 99.8150 -2.7116 4.7461
Considering B sucks
>
> Dbench %improvements
> ====================
> overcommit A B C
> 0.5x 3.2617 3.5436 2.5676
> 1.0x 0.6302 2.2342 5.2201
> 1.5x 5.0027 4.8275 3.8375
> 2.0x 23.8242 4.5782 12.6067
>
> Absolute values of base results: (overcommit, value, stdev)
> Ebizzy ( records / sec with 120 sec run)
> 0.5x 20941.8750 (2%)
> 1.0x 17623.8750 (5%)
> 1.5x 5874.7778 (15%)
> 2.0x 3581.8750 (7%)
>
> Dbench (throughput in MB/sec)
> 0.5x 10009.6610 (5%)
> 1.0x 6583.0538 (1%)
> 1.5x 3991.9622 (4%)
> 2.0x 2527.0613 (2.5%)
>
> Signed-off-by: Waiman Long <Waiman.Long@...com>
> Tested-by: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
> ---
> arch/x86/kernel/kvm.c | 135 +++++++++++++++++++++++++++++++++++++++++++++++++
> kernel/Kconfig.locks | 2 +-
> 2 files changed, 136 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 7ab8ab3..eef427b 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -567,6 +567,7 @@ static void kvm_kick_cpu(int cpu)
> kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid);
> }
>
> +#ifndef CONFIG_QUEUE_SPINLOCK
> enum kvm_contention_stat {
> TAKEN_SLOW,
> TAKEN_SLOW_PICKUP,
> @@ -794,6 +795,134 @@ static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket)
> }
> }
> }
> +#else /* !CONFIG_QUEUE_SPINLOCK */
> +
> +#ifdef CONFIG_KVM_DEBUG_FS
> +static struct dentry *d_spin_debug;
> +static struct dentry *d_kvm_debug;
> +static u32 kick_nohlt_stats; /* Kick but not halt count */
> +static u32 halt_qhead_stats; /* Queue head halting count */
> +static u32 halt_qnode_stats; /* Queue node halting count */
> +static u32 halt_abort_stats; /* Halting abort count */
> +static u32 wake_kick_stats; /* Wakeup by kicking count */
> +static u32 wake_spur_stats; /* Spurious wakeup count */
> +static u64 time_blocked; /* Total blocking time */
> +
> +static int __init kvm_spinlock_debugfs(void)
> +{
> + d_kvm_debug = debugfs_create_dir("kvm-guest", NULL);
> + if (!d_kvm_debug) {
> + printk(KERN_WARNING
> + "Could not create 'kvm' debugfs directory\n");
> + return -ENOMEM;
> + }
> + d_spin_debug = debugfs_create_dir("spinlocks", d_kvm_debug);
> +
> + debugfs_create_u32("kick_nohlt_stats",
> + 0644, d_spin_debug, &kick_nohlt_stats);
> + debugfs_create_u32("halt_qhead_stats",
> + 0644, d_spin_debug, &halt_qhead_stats);
> + debugfs_create_u32("halt_qnode_stats",
> + 0644, d_spin_debug, &halt_qnode_stats);
> + debugfs_create_u32("halt_abort_stats",
> + 0644, d_spin_debug, &halt_abort_stats);
> + debugfs_create_u32("wake_kick_stats",
> + 0644, d_spin_debug, &wake_kick_stats);
> + debugfs_create_u32("wake_spur_stats",
> + 0644, d_spin_debug, &wake_spur_stats);
> + debugfs_create_u64("time_blocked",
> + 0644, d_spin_debug, &time_blocked);
> + return 0;
> +}
> +
> +static inline void kvm_halt_stats(enum pv_lock_stats type)
> +{
> + if (type == PV_HALT_QHEAD)
> + add_smp(&halt_qhead_stats, 1);
> + else if (type == PV_HALT_QNODE)
> + add_smp(&halt_qnode_stats, 1);
> + else /* type == PV_HALT_ABORT */
> + add_smp(&halt_abort_stats, 1);
> +}
> +
> +static inline void kvm_lock_stats(enum pv_lock_stats type)
> +{
> + if (type == PV_WAKE_KICKED)
> + add_smp(&wake_kick_stats, 1);
> + else if (type == PV_WAKE_SPURIOUS)
> + add_smp(&wake_spur_stats, 1);
> + else /* type == PV_KICK_NOHALT */
> + add_smp(&kick_nohlt_stats, 1);
> +}
> +
> +static inline u64 spin_time_start(void)
> +{
> + return sched_clock();
> +}
> +
> +static inline void spin_time_accum_blocked(u64 start)
> +{
> + u64 delta;
> +
> + delta = sched_clock() - start;
> + add_smp(&time_blocked, delta);
> +}
> +
> +fs_initcall(kvm_spinlock_debugfs);
> +
> +#else /* CONFIG_KVM_DEBUG_FS */
> +static inline void kvm_halt_stats(enum pv_lock_stats type)
> +{
> +}
> +
> +static inline void kvm_lock_stats(enum pv_lock_stats type)
> +{
> +}
> +
> +static inline u64 spin_time_start(void)
> +{
> + return 0;
> +}
> +
> +static inline void spin_time_accum_blocked(u64 start)
> +{
> +}
> +#endif /* CONFIG_KVM_DEBUG_FS */
> +
> +/*
> + * Halt the current CPU & release it back to the host
> + */
> +static void kvm_halt_cpu(enum pv_lock_stats type, s8 *state, s8 sval)
> +{
> + unsigned long flags;
> + u64 start;
> +
> + if (in_nmi())
> + return;
> +
> + /*
> + * Make sure an interrupt handler can't upset things in a
> + * partially setup state.
> + */
> + local_irq_save(flags);
> + /*
> + * Don't halt if the CPU state has been changed.
> + */
> + if (ACCESS_ONCE(*state) != sval) {
> + kvm_halt_stats(PV_HALT_ABORT);
> + goto out;
> + }
> + start = spin_time_start();
> + kvm_halt_stats(type);
> + if (arch_irqs_disabled_flags(flags))
> + halt();
> + else
> + safe_halt();
> + spin_time_accum_blocked(start);
> +out:
> + local_irq_restore(flags);
> +}
> +#endif /* !CONFIG_QUEUE_SPINLOCK */
>
> /*
> * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.
> @@ -806,8 +935,14 @@ void __init kvm_spinlock_init(void)
> if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
> return;
>
> +#ifdef CONFIG_QUEUE_SPINLOCK
> + pv_lock_ops.kick_cpu = kvm_kick_cpu;
> + pv_lock_ops.halt_cpu = kvm_halt_cpu;
> + pv_lock_ops.lockstat = kvm_lock_stats;
> +#else
> pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning);
> pv_lock_ops.unlock_kick = kvm_unlock_kick;
> +#endif
> }
>
> static __init int kvm_spinlock_init_jump(void)
> diff --git a/kernel/Kconfig.locks b/kernel/Kconfig.locks
> index f185584..a70fdeb 100644
> --- a/kernel/Kconfig.locks
> +++ b/kernel/Kconfig.locks
> @@ -229,4 +229,4 @@ config ARCH_USE_QUEUE_SPINLOCK
>
> config QUEUE_SPINLOCK
> def_bool y if ARCH_USE_QUEUE_SPINLOCK
> - depends on SMP && !PARAVIRT_SPINLOCKS
> + depends on SMP && (!PARAVIRT_SPINLOCKS || !XEN)
> --
> 1.7.1
>
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