From: Nicholas Piggin <npiggin@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Nicholas Piggin <npiggin@gmail.com>,
Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
"Gautham R . Shenoy" <ego@linux.vnet.ibm.com>,
Paul Mackerras <paulus@ozlabs.org>
Subject: [PATCH 2/3] powerpc/64s/idle: avoid sync for KVM state when waking from idle
Date: Sat, 18 Nov 2017 00:08:06 +1000 [thread overview]
Message-ID: <20171117140807.22105-3-npiggin@gmail.com> (raw)
In-Reply-To: <20171117140807.22105-1-npiggin@gmail.com>
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>
---
arch/powerpc/kernel/idle_book3s.S | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 2f8364e7b489..07a306173c5a 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -532,6 +532,9 @@ 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 */
--
2.15.0
next prev parent reply other threads:[~2017-11-17 14:09 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-17 14:08 [PATCH 0/3] one more try at idle improvements Nicholas Piggin
2017-11-17 14:08 ` [PATCH 1/3] powerpc/64s/idle: POWER9 implement a separate idle stop function for hotplug Nicholas Piggin
2018-02-28 18:24 ` Vaidyanathan Srinivasan
2018-04-03 16:03 ` [1/3] " Michael Ellerman
2018-04-03 17:13 ` Nicholas Piggin
2018-04-04 12:52 ` Michael Ellerman
2017-11-17 14:08 ` Nicholas Piggin [this message]
2018-02-28 18:16 ` [PATCH 2/3] powerpc/64s/idle: avoid sync for KVM state when waking from idle Vaidyanathan Srinivasan
2018-03-01 11:38 ` Nicholas Piggin
2018-04-03 16:03 ` [2/3] " Michael Ellerman
2017-11-17 14:08 ` [PATCH 3/3] powerpc/64s/idle: POWER9 ESL=0 stop avoid save/restore overhead Nicholas Piggin
2018-02-28 18:34 ` Vaidyanathan Srinivasan
2018-03-01 11:57 ` Nicholas Piggin
2018-03-04 23:01 ` Paul Mackerras
2018-03-05 9:59 ` Nicholas Piggin
2018-03-31 11:46 ` Michael Ellerman
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