* [PATCH] powerpc, perf: Clear out branch entries to avoid any previous stale values
@ 2013-05-06 6:59 Anshuman Khandual
0 siblings, 0 replies; 5+ messages in thread
From: Anshuman Khandual @ 2013-05-06 6:59 UTC (permalink / raw)
To: linuxppc-dev; +Cc: mikey
The 'to' field inside branch entries might contain stale values from previous
PMU interrupt instances which had indirect branches. So clear all the values
before reading a fresh set of BHRB entries after a PMU interrupt.
Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
---
arch/powerpc/perf/core-book3s.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index c627843..09db68d 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1590,6 +1590,8 @@ static void record_and_restart(struct perf_event *event, unsigned long val,
if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) {
struct cpu_hw_events *cpuhw;
cpuhw = &__get_cpu_var(cpu_hw_events);
+ memset(cpuhw->bhrb_entries, 0,
+ sizeof(struct perf_branch_entry) * BHRB_MAX_ENTRIES);
power_pmu_bhrb_read(cpuhw);
data.br_stack = &cpuhw->bhrb_stack;
}
--
1.7.11.7
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] powerpc, perf: Clear out branch entries to avoid any previous stale values
2013-05-06 8:04 ` Anshuman Khandual
@ 2013-05-06 12:53 ` Michael Ellerman
-1 siblings, 0 replies; 5+ messages in thread
From: Michael Ellerman @ 2013-05-06 12:53 UTC (permalink / raw)
To: Anshuman Khandual; +Cc: linuxppc-dev, linux-kernel, mikey, benh
On Mon, 2013-05-06 at 13:34 +0530, Anshuman Khandual wrote:
> The 'to' field inside branch entries might contain stale values from previous
> PMU interrupt instances which had indirect branches. So clear all the values
> before reading a fresh set of BHRB entries after a PMU interrupt.
>
> Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
> ---
> arch/powerpc/perf/core-book3s.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
> index c627843..09db68d 100644
> --- a/arch/powerpc/perf/core-book3s.c
> +++ b/arch/powerpc/perf/core-book3s.c
> @@ -1590,6 +1590,8 @@ static void record_and_restart(struct perf_event *event, unsigned long val,
> if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) {
> struct cpu_hw_events *cpuhw;
> cpuhw = &__get_cpu_var(cpu_hw_events);
> + memset(cpuhw->bhrb_entries, 0,
> + sizeof(struct perf_branch_entry) * BHRB_MAX_ENTRIES);
> power_pmu_bhrb_read(cpuhw);
> data.br_stack = &cpuhw->bhrb_stack;
> }
Wouldn't it be just as effective, and less overhead, to set .to = 0; in
the else branch in power_pmu_bhrb_read() ?
eg:
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index c627843..30af11a4 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1516,6 +1516,7 @@ void power_pmu_bhrb_read(struct cpu_hw_events *cpuhw)
} else {
/* Update address, flags for current entry */
cpuhw->bhrb_entries[u_index].from = addr;
+ cpuhw->bhrb_entries[u_index].to = 0;
cpuhw->bhrb_entries[u_index].mispred = pred;
cpuhw->bhrb_entries[u_index].predicted = ~pred;
cheers
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] powerpc, perf: Clear out branch entries to avoid any previous stale values
@ 2013-05-06 12:53 ` Michael Ellerman
0 siblings, 0 replies; 5+ messages in thread
From: Michael Ellerman @ 2013-05-06 12:53 UTC (permalink / raw)
To: Anshuman Khandual; +Cc: linuxppc-dev, mikey, linux-kernel
On Mon, 2013-05-06 at 13:34 +0530, Anshuman Khandual wrote:
> The 'to' field inside branch entries might contain stale values from previous
> PMU interrupt instances which had indirect branches. So clear all the values
> before reading a fresh set of BHRB entries after a PMU interrupt.
>
> Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
> ---
> arch/powerpc/perf/core-book3s.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
> index c627843..09db68d 100644
> --- a/arch/powerpc/perf/core-book3s.c
> +++ b/arch/powerpc/perf/core-book3s.c
> @@ -1590,6 +1590,8 @@ static void record_and_restart(struct perf_event *event, unsigned long val,
> if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) {
> struct cpu_hw_events *cpuhw;
> cpuhw = &__get_cpu_var(cpu_hw_events);
> + memset(cpuhw->bhrb_entries, 0,
> + sizeof(struct perf_branch_entry) * BHRB_MAX_ENTRIES);
> power_pmu_bhrb_read(cpuhw);
> data.br_stack = &cpuhw->bhrb_stack;
> }
Wouldn't it be just as effective, and less overhead, to set .to = 0; in
the else branch in power_pmu_bhrb_read() ?
eg:
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index c627843..30af11a4 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1516,6 +1516,7 @@ void power_pmu_bhrb_read(struct cpu_hw_events *cpuhw)
} else {
/* Update address, flags for current entry */
cpuhw->bhrb_entries[u_index].from = addr;
+ cpuhw->bhrb_entries[u_index].to = 0;
cpuhw->bhrb_entries[u_index].mispred = pred;
cpuhw->bhrb_entries[u_index].predicted = ~pred;
cheers
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH] powerpc, perf: Clear out branch entries to avoid any previous stale values
@ 2013-05-06 8:04 ` Anshuman Khandual
0 siblings, 0 replies; 5+ messages in thread
From: Anshuman Khandual @ 2013-05-06 8:04 UTC (permalink / raw)
To: linuxppc-dev, linux-kernel; +Cc: michael, mikey, benh
The 'to' field inside branch entries might contain stale values from previous
PMU interrupt instances which had indirect branches. So clear all the values
before reading a fresh set of BHRB entries after a PMU interrupt.
Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
---
arch/powerpc/perf/core-book3s.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index c627843..09db68d 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1590,6 +1590,8 @@ static void record_and_restart(struct perf_event *event, unsigned long val,
if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) {
struct cpu_hw_events *cpuhw;
cpuhw = &__get_cpu_var(cpu_hw_events);
+ memset(cpuhw->bhrb_entries, 0,
+ sizeof(struct perf_branch_entry) * BHRB_MAX_ENTRIES);
power_pmu_bhrb_read(cpuhw);
data.br_stack = &cpuhw->bhrb_stack;
}
--
1.7.11.7
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH] powerpc, perf: Clear out branch entries to avoid any previous stale values
@ 2013-05-06 8:04 ` Anshuman Khandual
0 siblings, 0 replies; 5+ messages in thread
From: Anshuman Khandual @ 2013-05-06 8:04 UTC (permalink / raw)
To: linuxppc-dev, linux-kernel; +Cc: mikey
The 'to' field inside branch entries might contain stale values from previous
PMU interrupt instances which had indirect branches. So clear all the values
before reading a fresh set of BHRB entries after a PMU interrupt.
Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
---
arch/powerpc/perf/core-book3s.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index c627843..09db68d 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1590,6 +1590,8 @@ static void record_and_restart(struct perf_event *event, unsigned long val,
if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) {
struct cpu_hw_events *cpuhw;
cpuhw = &__get_cpu_var(cpu_hw_events);
+ memset(cpuhw->bhrb_entries, 0,
+ sizeof(struct perf_branch_entry) * BHRB_MAX_ENTRIES);
power_pmu_bhrb_read(cpuhw);
data.br_stack = &cpuhw->bhrb_stack;
}
--
1.7.11.7
^ permalink raw reply related [flat|nested] 5+ messages in thread
end of thread, other threads:[~2013-05-06 12:54 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2013-05-06 6:59 [PATCH] powerpc, perf: Clear out branch entries to avoid any previous stale values Anshuman Khandual
2013-05-06 8:04 Anshuman Khandual
2013-05-06 8:04 ` Anshuman Khandual
2013-05-06 12:53 ` Michael Ellerman
2013-05-06 12:53 ` Michael Ellerman
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