Commit 8c1c7fb0 authored Nov 18, 2017 by Nicholas Piggin Committed by Michael Ellerman Apr 01, 2018

powerpc/64s/idle: avoid sync for KVM state when waking from idle



When waking from a CPU idle instruction (e.g., nap or stop), the sync
for ordering the KVM secondary thread state can be avoided if there
wakeup is coming from a kernel context rather than KVM context.

This improves performance for ping-pong benchmark with the stop0 idle
state by 0.46% for 2 threads in the same core, and 1.02% for different
cores.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

parent 3d4fbffd

arch/powerpc/kernel/idle_book3s.S

+3 −0

Original line number	Diff line number	Diff line
		@@ -551,6 +551,9 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_ARCH_300)
		mr r3,r12

		#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
		lbz r0,HSTATE_HWTHREAD_STATE(r13)
		cmpwi r0,KVM_HWTHREAD_IN_KERNEL
		beq 1f
		li r0,KVM_HWTHREAD_IN_KERNEL
		stb r0,HSTATE_HWTHREAD_STATE(r13)
		/* Order setting hwthread_state vs. testing hwthread_req */