>From c79b86d00a812d6207ef788d453e2d0289ef22a0 Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Wed, 19 Oct 2016 15:30:59 +0200 Subject: [PATCH] x86, xen: support vcpu preempted check Support the vcpu_is_preempted() functionality under Xen. This will enhance lock performance on overcommitted hosts (more runnable vcpus than physical cpus in the system) as doing busy waits for preempted vcpus will hurt system performance far worse than early yielding. A quick test (4 vcpus on 1 physical cpu doing a parallel build job with "make -j 8") reduced system time by about 5% with this patch. Signed-off-by: Juergen Gross --- arch/x86/xen/spinlock.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c index 3d6e006..1d53b1b 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -114,7 +114,6 @@ void xen_uninit_lock_cpu(int cpu) per_cpu(irq_name, cpu) = NULL; } - /* * Our init of PV spinlocks is split in two init functions due to us * using paravirt patching and jump labels patching and having to do @@ -137,6 +136,8 @@ void __init xen_init_spinlocks(void) pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock); pv_lock_ops.wait = xen_qlock_wait; pv_lock_ops.kick = xen_qlock_kick; + + pv_vcpu_ops.vcpu_is_preempted = xen_vcpu_stolen; } /* -- 2.6.6