Commit de7689cf authored Nov 02, 2016 by Juergen Gross Committed by Ingo Molnar Nov 22, 2016

x86/xen: Support the vCPU preemption 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 <jgross@suse.com>
Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: David.Laight@ACULAB.COM
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: benh@kernel.crashing.org
Cc: boqun.feng@gmail.com
Cc: borntraeger@de.ibm.com
Cc: bsingharora@gmail.com
Cc: dave@stgolabs.net
Cc: kernellwp@gmail.com
Cc: konrad.wilk@oracle.com
Cc: linuxppc-dev@lists.ozlabs.org
Cc: mpe@ellerman.id.au
Cc: paulmck@linux.vnet.ibm.com
Cc: paulus@samba.org
Cc: pbonzini@redhat.com
Cc: rkrcmar@redhat.com
Cc: virtualization@lists.linux-foundation.org
Cc: will.deacon@arm.com
Cc: xen-devel-request@lists.xenproject.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1478077718-37424-11-git-send-email-xinhui.pan@linux.vnet.ibm.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 1885aa70

arch/x86/xen/spinlock.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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_lock_ops.vcpu_is_preempted = xen_vcpu_stolen;
		}

		/*

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