* [PATCH 1/4] powerpc: Refactor is_kvm_guest declaration to new header
2020-10-28 12:35 [PATCH 0/4] Powerpc: Better preemption for shared processor Srikar Dronamraju
@ 2020-10-28 12:35 ` Srikar Dronamraju
2020-10-28 12:35 ` [PATCH 2/4] powerpc: Rename is_kvm_guest to check_kvm_guest Srikar Dronamraju
` (3 subsequent siblings)
4 siblings, 0 replies; 7+ messages in thread
From: Srikar Dronamraju @ 2020-10-28 12:35 UTC (permalink / raw)
To: Michael Ellerman
Cc: Nathan Lynch, Gautham R Shenoy, Phil Auld, Srikar Dronamraju,
Juri Lelli, Peter Zijlstra, LKML, Nicholas Piggin, Waiman Long,
linuxppc-dev, Valentin Schneider
Only code/declaration movement, in anticipation of doing a kvm-aware
vcpu_is_preempted. No additional changes.
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Phil Auld <pauld@redhat.com>
---
arch/powerpc/include/asm/firmware.h | 6 ------
arch/powerpc/include/asm/kvm_guest.h | 15 +++++++++++++++
arch/powerpc/include/asm/kvm_para.h | 2 +-
arch/powerpc/platforms/pseries/smp.c | 1 +
4 files changed, 17 insertions(+), 7 deletions(-)
create mode 100644 arch/powerpc/include/asm/kvm_guest.h
diff --git a/arch/powerpc/include/asm/firmware.h b/arch/powerpc/include/asm/firmware.h
index 0b295bdb201e..aa6a5ef5d483 100644
--- a/arch/powerpc/include/asm/firmware.h
+++ b/arch/powerpc/include/asm/firmware.h
@@ -134,12 +134,6 @@ extern int ibm_nmi_interlock_token;
extern unsigned int __start___fw_ftr_fixup, __stop___fw_ftr_fixup;
-#if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_KVM_GUEST)
-bool is_kvm_guest(void);
-#else
-static inline bool is_kvm_guest(void) { return false; }
-#endif
-
#ifdef CONFIG_PPC_PSERIES
void pseries_probe_fw_features(void);
#else
diff --git a/arch/powerpc/include/asm/kvm_guest.h b/arch/powerpc/include/asm/kvm_guest.h
new file mode 100644
index 000000000000..c0ace884a0e8
--- /dev/null
+++ b/arch/powerpc/include/asm/kvm_guest.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 IBM Corporation
+ */
+
+#ifndef __POWERPC_KVM_GUEST_H__
+#define __POWERPC_KVM_GUEST_H__
+
+#if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_KVM_GUEST)
+bool is_kvm_guest(void);
+#else
+static inline bool is_kvm_guest(void) { return false; }
+#endif
+
+#endif /* __POWERPC_KVM_GUEST_H__ */
diff --git a/arch/powerpc/include/asm/kvm_para.h b/arch/powerpc/include/asm/kvm_para.h
index 744612054c94..abe1b5e82547 100644
--- a/arch/powerpc/include/asm/kvm_para.h
+++ b/arch/powerpc/include/asm/kvm_para.h
@@ -8,7 +8,7 @@
#ifndef __POWERPC_KVM_PARA_H__
#define __POWERPC_KVM_PARA_H__
-#include <asm/firmware.h>
+#include <asm/kvm_guest.h>
#include <uapi/asm/kvm_para.h>
diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c
index 92922491a81c..d578732c545d 100644
--- a/arch/powerpc/platforms/pseries/smp.c
+++ b/arch/powerpc/platforms/pseries/smp.c
@@ -42,6 +42,7 @@
#include <asm/plpar_wrappers.h>
#include <asm/code-patching.h>
#include <asm/svm.h>
+#include <asm/kvm_guest.h>
#include "pseries.h"
--
2.18.4
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH 2/4] powerpc: Rename is_kvm_guest to check_kvm_guest
2020-10-28 12:35 [PATCH 0/4] Powerpc: Better preemption for shared processor Srikar Dronamraju
2020-10-28 12:35 ` [PATCH 1/4] powerpc: Refactor is_kvm_guest declaration to new header Srikar Dronamraju
@ 2020-10-28 12:35 ` Srikar Dronamraju
2020-10-28 12:35 ` [PATCH 3/4] powerpc: Reintroduce is_kvm_guest in a new avatar Srikar Dronamraju
` (2 subsequent siblings)
4 siblings, 0 replies; 7+ messages in thread
From: Srikar Dronamraju @ 2020-10-28 12:35 UTC (permalink / raw)
To: Michael Ellerman
Cc: Nathan Lynch, Gautham R Shenoy, Phil Auld, Srikar Dronamraju,
Juri Lelli, Peter Zijlstra, LKML, Nicholas Piggin, Waiman Long,
linuxppc-dev, Valentin Schneider
is_kvm_guest() will be reused in subsequent patch in a new avatar. Hence
rename is_kvm_guest to check_kvm_guest. No additional changes.
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Phil Auld <pauld@redhat.com>
---
arch/powerpc/include/asm/kvm_guest.h | 4 ++--
arch/powerpc/include/asm/kvm_para.h | 2 +-
arch/powerpc/kernel/firmware.c | 2 +-
arch/powerpc/platforms/pseries/smp.c | 2 +-
4 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/include/asm/kvm_guest.h b/arch/powerpc/include/asm/kvm_guest.h
index c0ace884a0e8..ba8291e02ba9 100644
--- a/arch/powerpc/include/asm/kvm_guest.h
+++ b/arch/powerpc/include/asm/kvm_guest.h
@@ -7,9 +7,9 @@
#define __POWERPC_KVM_GUEST_H__
#if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_KVM_GUEST)
-bool is_kvm_guest(void);
+bool check_kvm_guest(void);
#else
-static inline bool is_kvm_guest(void) { return false; }
+static inline bool check_kvm_guest(void) { return false; }
#endif
#endif /* __POWERPC_KVM_GUEST_H__ */
diff --git a/arch/powerpc/include/asm/kvm_para.h b/arch/powerpc/include/asm/kvm_para.h
index abe1b5e82547..6fba06b6cfdb 100644
--- a/arch/powerpc/include/asm/kvm_para.h
+++ b/arch/powerpc/include/asm/kvm_para.h
@@ -14,7 +14,7 @@
static inline int kvm_para_available(void)
{
- return IS_ENABLED(CONFIG_KVM_GUEST) && is_kvm_guest();
+ return IS_ENABLED(CONFIG_KVM_GUEST) && check_kvm_guest();
}
static inline unsigned int kvm_arch_para_features(void)
diff --git a/arch/powerpc/kernel/firmware.c b/arch/powerpc/kernel/firmware.c
index fe48d319d490..61243267d4cf 100644
--- a/arch/powerpc/kernel/firmware.c
+++ b/arch/powerpc/kernel/firmware.c
@@ -21,7 +21,7 @@ EXPORT_SYMBOL_GPL(powerpc_firmware_features);
#endif
#if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_KVM_GUEST)
-bool is_kvm_guest(void)
+bool check_kvm_guest(void)
{
struct device_node *hyper_node;
diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c
index d578732c545d..c70b4be9f0a5 100644
--- a/arch/powerpc/platforms/pseries/smp.c
+++ b/arch/powerpc/platforms/pseries/smp.c
@@ -211,7 +211,7 @@ static __init void pSeries_smp_probe(void)
if (!cpu_has_feature(CPU_FTR_SMT))
return;
- if (is_kvm_guest()) {
+ if (check_kvm_guest()) {
/*
* KVM emulates doorbells by disabling FSCR[MSGP] so msgsndp
* faults to the hypervisor which then reads the instruction
--
2.18.4
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH 3/4] powerpc: Reintroduce is_kvm_guest in a new avatar
2020-10-28 12:35 [PATCH 0/4] Powerpc: Better preemption for shared processor Srikar Dronamraju
2020-10-28 12:35 ` [PATCH 1/4] powerpc: Refactor is_kvm_guest declaration to new header Srikar Dronamraju
2020-10-28 12:35 ` [PATCH 2/4] powerpc: Rename is_kvm_guest to check_kvm_guest Srikar Dronamraju
@ 2020-10-28 12:35 ` Srikar Dronamraju
2020-10-28 12:35 ` [PATCH 4/4] powerpc/paravirt: Use is_kvm_guest in vcpu_is_preempted Srikar Dronamraju
2020-10-29 0:01 ` [PATCH 0/4] Powerpc: Better preemption for shared processor Waiman Long
4 siblings, 0 replies; 7+ messages in thread
From: Srikar Dronamraju @ 2020-10-28 12:35 UTC (permalink / raw)
To: Michael Ellerman
Cc: Nathan Lynch, Gautham R Shenoy, Phil Auld, Srikar Dronamraju,
Juri Lelli, Peter Zijlstra, LKML, Nicholas Piggin, Waiman Long,
linuxppc-dev, Valentin Schneider
Introduce a static branch that would be set during boot if the OS
happens to be a KVM guest. Subsequent checks to see if we are on KVM
will rely on this static branch. This static branch would be used in
vcpu_is_preempted in a subsequent patch.
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Phil Auld <pauld@redhat.com>
---
arch/powerpc/include/asm/kvm_guest.h | 10 ++++++++++
arch/powerpc/include/asm/kvm_para.h | 2 +-
arch/powerpc/kernel/firmware.c | 3 +++
3 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/kvm_guest.h b/arch/powerpc/include/asm/kvm_guest.h
index ba8291e02ba9..627ba272e781 100644
--- a/arch/powerpc/include/asm/kvm_guest.h
+++ b/arch/powerpc/include/asm/kvm_guest.h
@@ -7,8 +7,18 @@
#define __POWERPC_KVM_GUEST_H__
#if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_KVM_GUEST)
+#include <linux/jump_label.h>
+
+DECLARE_STATIC_KEY_FALSE(kvm_guest);
+
+static inline bool is_kvm_guest(void)
+{
+ return static_branch_unlikely(&kvm_guest);
+}
+
bool check_kvm_guest(void);
#else
+static inline bool is_kvm_guest(void) { return false; }
static inline bool check_kvm_guest(void) { return false; }
#endif
diff --git a/arch/powerpc/include/asm/kvm_para.h b/arch/powerpc/include/asm/kvm_para.h
index 6fba06b6cfdb..abe1b5e82547 100644
--- a/arch/powerpc/include/asm/kvm_para.h
+++ b/arch/powerpc/include/asm/kvm_para.h
@@ -14,7 +14,7 @@
static inline int kvm_para_available(void)
{
- return IS_ENABLED(CONFIG_KVM_GUEST) && check_kvm_guest();
+ return IS_ENABLED(CONFIG_KVM_GUEST) && is_kvm_guest();
}
static inline unsigned int kvm_arch_para_features(void)
diff --git a/arch/powerpc/kernel/firmware.c b/arch/powerpc/kernel/firmware.c
index 61243267d4cf..28498fc573f2 100644
--- a/arch/powerpc/kernel/firmware.c
+++ b/arch/powerpc/kernel/firmware.c
@@ -14,6 +14,7 @@
#include <linux/of.h>
#include <asm/firmware.h>
+#include <asm/kvm_guest.h>
#ifdef CONFIG_PPC64
unsigned long powerpc_firmware_features __read_mostly;
@@ -21,6 +22,7 @@ EXPORT_SYMBOL_GPL(powerpc_firmware_features);
#endif
#if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_KVM_GUEST)
+DEFINE_STATIC_KEY_FALSE(kvm_guest);
bool check_kvm_guest(void)
{
struct device_node *hyper_node;
@@ -32,6 +34,7 @@ bool check_kvm_guest(void)
if (!of_device_is_compatible(hyper_node, "linux,kvm"))
return 0;
+ static_branch_enable(&kvm_guest);
return 1;
}
#endif
--
2.18.4
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH 4/4] powerpc/paravirt: Use is_kvm_guest in vcpu_is_preempted
2020-10-28 12:35 [PATCH 0/4] Powerpc: Better preemption for shared processor Srikar Dronamraju
` (2 preceding siblings ...)
2020-10-28 12:35 ` [PATCH 3/4] powerpc: Reintroduce is_kvm_guest in a new avatar Srikar Dronamraju
@ 2020-10-28 12:35 ` Srikar Dronamraju
2020-10-29 0:01 ` [PATCH 0/4] Powerpc: Better preemption for shared processor Waiman Long
4 siblings, 0 replies; 7+ messages in thread
From: Srikar Dronamraju @ 2020-10-28 12:35 UTC (permalink / raw)
To: Michael Ellerman
Cc: Nathan Lynch, Gautham R Shenoy, Phil Auld, Srikar Dronamraju,
Juri Lelli, Peter Zijlstra, LKML, Nicholas Piggin, Waiman Long,
linuxppc-dev, Valentin Schneider
If its a shared lpar but not a KVM guest, then see if the vCPU is
related to the calling vCPU. On PowerVM, only cores can be preempted.
So if one vCPU is a non-preempted state, we can decipher that all other
vCPUs sharing the same core are in non-preempted state.
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Phil Auld <pauld@redhat.com>
---
arch/powerpc/include/asm/paravirt.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/arch/powerpc/include/asm/paravirt.h b/arch/powerpc/include/asm/paravirt.h
index 9362c94fe3aa..edc08f04aef7 100644
--- a/arch/powerpc/include/asm/paravirt.h
+++ b/arch/powerpc/include/asm/paravirt.h
@@ -10,6 +10,9 @@
#endif
#ifdef CONFIG_PPC_SPLPAR
+#include <asm/kvm_guest.h>
+#include <asm/cputhreads.h>
+
DECLARE_STATIC_KEY_FALSE(shared_processor);
static inline bool is_shared_processor(void)
@@ -74,6 +77,21 @@ static inline bool vcpu_is_preempted(int cpu)
{
if (!is_shared_processor())
return false;
+
+#ifdef CONFIG_PPC_SPLPAR
+ if (!is_kvm_guest()) {
+ int first_cpu = cpu_first_thread_sibling(smp_processor_id());
+
+ /*
+ * Preemption can only happen at core granularity. This CPU
+ * is not preempted if one of the CPU of this core is not
+ * preempted.
+ */
+ if (cpu_first_thread_sibling(cpu) == first_cpu)
+ return false;
+ }
+#endif
+
if (yield_count_of(cpu) & 1)
return true;
return false;
--
2.18.4
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH 0/4] Powerpc: Better preemption for shared processor
2020-10-28 12:35 [PATCH 0/4] Powerpc: Better preemption for shared processor Srikar Dronamraju
` (3 preceding siblings ...)
2020-10-28 12:35 ` [PATCH 4/4] powerpc/paravirt: Use is_kvm_guest in vcpu_is_preempted Srikar Dronamraju
@ 2020-10-29 0:01 ` Waiman Long
2020-10-29 7:14 ` Srikar Dronamraju
4 siblings, 1 reply; 7+ messages in thread
From: Waiman Long @ 2020-10-29 0:01 UTC (permalink / raw)
To: Srikar Dronamraju, Michael Ellerman
Cc: Nathan Lynch, Gautham R Shenoy, Phil Auld, Juri Lelli,
Peter Zijlstra, LKML, Nicholas Piggin, linuxppc-dev,
Valentin Schneider
On 10/28/20 8:35 AM, Srikar Dronamraju wrote:
> Currently, vcpu_is_preempted will return the yield_count for
> shared_processor. On a PowerVM LPAR, Phyp schedules at SMT8 core boundary
> i.e all CPUs belonging to a core are either group scheduled in or group
> scheduled out. This can be used to better predict non-preempted CPUs on
> PowerVM shared LPARs.
>
> perf stat -r 5 -a perf bench sched pipe -l 10000000 (lesser time is better)
>
> powerpc/next
> 35,107,951.20 msec cpu-clock # 255.898 CPUs utilized ( +- 0.31% )
> 23,655,348 context-switches # 0.674 K/sec ( +- 3.72% )
> 14,465 cpu-migrations # 0.000 K/sec ( +- 5.37% )
> 82,463 page-faults # 0.002 K/sec ( +- 8.40% )
> 1,127,182,328,206 cycles # 0.032 GHz ( +- 1.60% ) (66.67%)
> 78,587,300,622 stalled-cycles-frontend # 6.97% frontend cycles idle ( +- 0.08% ) (50.01%)
> 654,124,218,432 stalled-cycles-backend # 58.03% backend cycles idle ( +- 1.74% ) (50.01%)
> 834,013,059,242 instructions # 0.74 insn per cycle
> # 0.78 stalled cycles per insn ( +- 0.73% ) (66.67%)
> 132,911,454,387 branches # 3.786 M/sec ( +- 0.59% ) (50.00%)
> 2,890,882,143 branch-misses # 2.18% of all branches ( +- 0.46% ) (50.00%)
>
> 137.195 +- 0.419 seconds time elapsed ( +- 0.31% )
>
> powerpc/next + patchset
> 29,981,702.64 msec cpu-clock # 255.881 CPUs utilized ( +- 1.30% )
> 40,162,456 context-switches # 0.001 M/sec ( +- 0.01% )
> 1,110 cpu-migrations # 0.000 K/sec ( +- 5.20% )
> 62,616 page-faults # 0.002 K/sec ( +- 3.93% )
> 1,430,030,626,037 cycles # 0.048 GHz ( +- 1.41% ) (66.67%)
> 83,202,707,288 stalled-cycles-frontend # 5.82% frontend cycles idle ( +- 0.75% ) (50.01%)
> 744,556,088,520 stalled-cycles-backend # 52.07% backend cycles idle ( +- 1.39% ) (50.01%)
> 940,138,418,674 instructions # 0.66 insn per cycle
> # 0.79 stalled cycles per insn ( +- 0.51% ) (66.67%)
> 146,452,852,283 branches # 4.885 M/sec ( +- 0.80% ) (50.00%)
> 3,237,743,996 branch-misses # 2.21% of all branches ( +- 1.18% ) (50.01%)
>
> 117.17 +- 1.52 seconds time elapsed ( +- 1.30% )
>
> This is around 14.6% improvement in performance.
>
> Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
> Cc: LKML <linux-kernel@vger.kernel.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Nathan Lynch <nathanl@linux.ibm.com>
> Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Valentin Schneider <valentin.schneider@arm.com>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Waiman Long <longman@redhat.com>
> Cc: Phil Auld <pauld@redhat.com>
>
> Srikar Dronamraju (4):
> powerpc: Refactor is_kvm_guest declaration to new header
> powerpc: Rename is_kvm_guest to check_kvm_guest
> powerpc: Reintroduce is_kvm_guest
> powerpc/paravirt: Use is_kvm_guest in vcpu_is_preempted
>
> arch/powerpc/include/asm/firmware.h | 6 ------
> arch/powerpc/include/asm/kvm_guest.h | 25 +++++++++++++++++++++++++
> arch/powerpc/include/asm/kvm_para.h | 2 +-
> arch/powerpc/include/asm/paravirt.h | 18 ++++++++++++++++++
> arch/powerpc/kernel/firmware.c | 5 ++++-
> arch/powerpc/platforms/pseries/smp.c | 3 ++-
> 6 files changed, 50 insertions(+), 9 deletions(-)
> create mode 100644 arch/powerpc/include/asm/kvm_guest.h
>
This patch series looks good to me and the performance is nice too.
Acked-by: Waiman Long <longman@redhat.com>
Just curious, is the performance mainly from the use of static_branch
(patches 1 - 3) or from reducing call to yield_count_of().
Cheers,
Longman
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH 0/4] Powerpc: Better preemption for shared processor
2020-10-29 0:01 ` [PATCH 0/4] Powerpc: Better preemption for shared processor Waiman Long
@ 2020-10-29 7:14 ` Srikar Dronamraju
0 siblings, 0 replies; 7+ messages in thread
From: Srikar Dronamraju @ 2020-10-29 7:14 UTC (permalink / raw)
To: Waiman Long
Cc: Nathan Lynch, Gautham R Shenoy, Phil Auld, Juri Lelli,
Peter Zijlstra, LKML, Nicholas Piggin, linuxppc-dev,
Valentin Schneider
* Waiman Long <longman@redhat.com> [2020-10-28 20:01:30]:
> > Srikar Dronamraju (4):
> > powerpc: Refactor is_kvm_guest declaration to new header
> > powerpc: Rename is_kvm_guest to check_kvm_guest
> > powerpc: Reintroduce is_kvm_guest
> > powerpc/paravirt: Use is_kvm_guest in vcpu_is_preempted
> >
> > arch/powerpc/include/asm/firmware.h | 6 ------
> > arch/powerpc/include/asm/kvm_guest.h | 25 +++++++++++++++++++++++++
> > arch/powerpc/include/asm/kvm_para.h | 2 +-
> > arch/powerpc/include/asm/paravirt.h | 18 ++++++++++++++++++
> > arch/powerpc/kernel/firmware.c | 5 ++++-
> > arch/powerpc/platforms/pseries/smp.c | 3 ++-
> > 6 files changed, 50 insertions(+), 9 deletions(-)
> > create mode 100644 arch/powerpc/include/asm/kvm_guest.h
> >
> This patch series looks good to me and the performance is nice too.
>
> Acked-by: Waiman Long <longman@redhat.com>
Thank you.
>
> Just curious, is the performance mainly from the use of static_branch
> (patches 1 - 3) or from reducing call to yield_count_of().
Because of the reduced call to yield_count
>
> Cheers,
> Longman
>
--
Thanks and Regards
Srikar Dronamraju
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