* [PATCH v3 0/3] perf: Add PERF_EVENT_IOC_INC_EVENT_LIMIT
@ 2025-01-07 4:07 Charlie Jenkins
2025-01-07 4:07 ` [PATCH v3 1/3] " Charlie Jenkins
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Charlie Jenkins @ 2025-01-07 4:07 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim, Mark Rutland, Alexander Shishkin, Jiri Olsa,
Ian Rogers, Adrian Hunter, Atish Patra
Cc: linux-perf-users, linux-kernel, Charlie Jenkins,
Shunsuke Nakamura
Introduce a new perf ioctl key PERF_EVENT_IOC_INC_EVENT_LIMIT that
functions the same as PERF_EVENT_IOC_REFRESH, except it does not
immediately enable counters.
Also create a libperf API perf_evsel__refresh() to allow libperf users
access to this ioctl key.
Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
This series is going to cause an issue conflict with another series I
sent [1]. The final patch of this series changes perf_evsel__ioctl() to
accept a unsigned long instead of void *. My preference would be for the
following patch to be squashed onto "libperf: Add perf_evsel__refresh()
function" when applied:
From 66ab7b57c8b5a94c02c8d82204338b0ebca48bc5 Mon Sep 17 00:00:00 2001
From: Charlie Jenkins <charlie@rivosinc.com>
Date: Mon, 6 Jan 2025 20:00:28 -0800
Subject: [PATCH] libperf: Fixup perf_evsel__get_id
This patch should be squashed onto
"libperf: Add perf_evsel__refresh() function" or
"libperf: Add perf_evsel__id() function" when merging.
Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
tools/lib/perf/evsel.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
index 1cd1680d28d7..8690588c0ba1 100644
--- a/tools/lib/perf/evsel.c
+++ b/tools/lib/perf/evsel.c
@@ -521,7 +521,7 @@ int perf_evsel__period(struct perf_evsel *evsel, u64 period)
static int perf_evsel__get_id(struct perf_evsel *evsel, int cpu_map_idx, int thread, u64 *id)
{
- return perf_evsel__ioctl(evsel, PERF_EVENT_IOC_ID, id, cpu_map_idx, thread);
+ return perf_evsel__ioctl(evsel, PERF_EVENT_IOC_ID, (unsigned long)id, cpu_map_idx, thread);
}
int perf_evsel__id(struct perf_evsel *evsel, u64 *ids[])
--
2.34.1
[1] https://lore.kernel.org/lkml/20250106-perf_evsel_get_id-v3-1-44eca9194f1e@rivosinc.com/T/#u
Changes in v3:
- Use uint64_t instead of __u64 for consistency
- Link to v2: https://lore.kernel.org/r/20240807-perf_set_event_limit-v2-0-823b78d04c76@rivosinc.com
Changes in v2:
- Drop discussion about signal race condition
- Add new patch "libperf: Add perf_evsel__refresh() function"
- This newly added patch was pulled from a different series with
modifications to fit the new ioctl key
-
https://lore.kernel.org/lkml/20240726-overflow_check_libperf-v2-0-7d154dcf6bea@rivosinc.com/
will be updated
- Link to v1: https://lore.kernel.org/r/20240724-perf_set_event_limit-v1-0-e680c93eca55@rivosinc.com
---
Charlie Jenkins (3):
perf: Add PERF_EVENT_IOC_INC_EVENT_LIMIT
perf: Document PERF_EVENT_IOC_INC_EVENT_LIMIT
libperf: Add perf_evsel__refresh() function
include/linux/perf_event.h | 4 +--
include/uapi/linux/perf_event.h | 1 +
kernel/events/core.c | 17 +++++++----
tools/include/uapi/linux/perf_event.h | 1 +
tools/lib/perf/Documentation/libperf.txt | 2 ++
tools/lib/perf/evsel.c | 49 ++++++++++++++++++++++++++------
tools/lib/perf/include/perf/evsel.h | 2 ++
tools/lib/perf/libperf.map | 2 ++
tools/perf/design.txt | 5 ++++
9 files changed, 67 insertions(+), 16 deletions(-)
---
base-commit: ed60738a9b7ede4a4ae797d90be7fde3e10a36c7
change-id: 20240724-perf_set_event_limit-079f1b996376
--
- Charlie
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v3 1/3] perf: Add PERF_EVENT_IOC_INC_EVENT_LIMIT
2025-01-07 4:07 [PATCH v3 0/3] perf: Add PERF_EVENT_IOC_INC_EVENT_LIMIT Charlie Jenkins
@ 2025-01-07 4:07 ` Charlie Jenkins
2025-01-13 13:18 ` Peter Zijlstra
2025-01-07 4:07 ` [PATCH v3 2/3] perf: Document PERF_EVENT_IOC_INC_EVENT_LIMIT Charlie Jenkins
2025-01-07 4:07 ` [PATCH v3 3/3] libperf: Add perf_evsel__refresh() function Charlie Jenkins
2 siblings, 1 reply; 6+ messages in thread
From: Charlie Jenkins @ 2025-01-07 4:07 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim, Mark Rutland, Alexander Shishkin, Jiri Olsa,
Ian Rogers, Adrian Hunter, Atish Patra
Cc: linux-perf-users, linux-kernel, Charlie Jenkins
PERF_EVENT_IOC_REFRESH immediately enables after incrementing
event_limit. Provide a new ioctl flag that allows programs to increment
event_limit without enabling the event. A usecase for this is to set an
event_limit in combination with enable_on_exec.
Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
include/linux/perf_event.h | 4 ++--
include/uapi/linux/perf_event.h | 1 +
kernel/events/core.c | 17 +++++++++++------
tools/include/uapi/linux/perf_event.h | 1 +
4 files changed, 15 insertions(+), 8 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index cb99ec8c9e96f63c64eeeb4470c019d86bc6e50f..9b407d51818f59e1548f8936ec0bb185fc4d9f0c 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1147,7 +1147,7 @@ extern int perf_event_task_enable(void);
extern void perf_pmu_resched(struct pmu *pmu);
-extern int perf_event_refresh(struct perf_event *event, int refresh);
+extern int perf_event_refresh(struct perf_event *event, int refresh, bool enable);
extern void perf_event_update_userpage(struct perf_event *event);
extern int perf_event_release_kernel(struct perf_event *event);
extern struct perf_event *
@@ -1835,7 +1835,7 @@ static inline int perf_event_read_local(struct perf_event *event, u64 *value,
static inline void perf_event_print_debug(void) { }
static inline int perf_event_task_disable(void) { return -EINVAL; }
static inline int perf_event_task_enable(void) { return -EINVAL; }
-static inline int perf_event_refresh(struct perf_event *event, int refresh)
+static inline int perf_event_refresh(struct perf_event *event, int refresh, bool enable)
{
return -EINVAL;
}
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 0524d541d4e3d50150da03186467382bc60bdf50..5eeccd57078c95f08f6ac401b1e38c2e84e86d9a 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -569,6 +569,7 @@ struct perf_event_query_bpf {
#define PERF_EVENT_IOC_PAUSE_OUTPUT _IOW('$', 9, __u32)
#define PERF_EVENT_IOC_QUERY_BPF _IOWR('$', 10, struct perf_event_query_bpf *)
#define PERF_EVENT_IOC_MODIFY_ATTRIBUTES _IOW('$', 11, struct perf_event_attr *)
+#define PERF_EVENT_IOC_INC_EVENT_LIMIT _IO ('$', 12)
enum perf_event_ioc_flags {
PERF_IOC_FLAG_GROUP = 1U << 0,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 065f9188b44a0d8ee66cc76314ae247dbe45cb57..6514065513ba01e99c88854f3947a114562e81ad 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3210,7 +3210,7 @@ void perf_event_addr_filters_sync(struct perf_event *event)
}
EXPORT_SYMBOL_GPL(perf_event_addr_filters_sync);
-static int _perf_event_refresh(struct perf_event *event, int refresh)
+static int _perf_event_refresh(struct perf_event *event, int refresh, bool enable)
{
/*
* not supported on inherited events
@@ -3219,7 +3219,8 @@ static int _perf_event_refresh(struct perf_event *event, int refresh)
return -EINVAL;
atomic_add(refresh, &event->event_limit);
- _perf_event_enable(event);
+ if (enable)
+ _perf_event_enable(event);
return 0;
}
@@ -3227,13 +3228,13 @@ static int _perf_event_refresh(struct perf_event *event, int refresh)
/*
* See perf_event_disable()
*/
-int perf_event_refresh(struct perf_event *event, int refresh)
+int perf_event_refresh(struct perf_event *event, int refresh, bool enable)
{
struct perf_event_context *ctx;
int ret;
ctx = perf_event_ctx_lock(event);
- ret = _perf_event_refresh(event, refresh);
+ ret = _perf_event_refresh(event, refresh, enable);
perf_event_ctx_unlock(event, ctx);
return ret;
@@ -6019,7 +6020,7 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon
break;
case PERF_EVENT_IOC_REFRESH:
- return _perf_event_refresh(event, arg);
+ return _perf_event_refresh(event, arg, true);
case PERF_EVENT_IOC_PERIOD:
{
@@ -6099,6 +6100,10 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon
return perf_event_modify_attr(event, &new_attr);
}
+
+ case PERF_EVENT_IOC_INC_EVENT_LIMIT:
+ return _perf_event_refresh(event, arg, false);
+
default:
return -ENOTTY;
}
@@ -6820,7 +6825,7 @@ void perf_event_wakeup(struct perf_event *event)
ring_buffer_wakeup(event);
if (event->pending_kill) {
- kill_fasync(perf_event_fasync(event), SIGIO, event->pending_kill);
+ kill_fasync(perf_event_fasync(event), SIGTRAP, event->pending_kill);
event->pending_kill = 0;
}
}
diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
index 0524d541d4e3d50150da03186467382bc60bdf50..5eeccd57078c95f08f6ac401b1e38c2e84e86d9a 100644
--- a/tools/include/uapi/linux/perf_event.h
+++ b/tools/include/uapi/linux/perf_event.h
@@ -569,6 +569,7 @@ struct perf_event_query_bpf {
#define PERF_EVENT_IOC_PAUSE_OUTPUT _IOW('$', 9, __u32)
#define PERF_EVENT_IOC_QUERY_BPF _IOWR('$', 10, struct perf_event_query_bpf *)
#define PERF_EVENT_IOC_MODIFY_ATTRIBUTES _IOW('$', 11, struct perf_event_attr *)
+#define PERF_EVENT_IOC_INC_EVENT_LIMIT _IO ('$', 12)
enum perf_event_ioc_flags {
PERF_IOC_FLAG_GROUP = 1U << 0,
--
2.34.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v3 2/3] perf: Document PERF_EVENT_IOC_INC_EVENT_LIMIT
2025-01-07 4:07 [PATCH v3 0/3] perf: Add PERF_EVENT_IOC_INC_EVENT_LIMIT Charlie Jenkins
2025-01-07 4:07 ` [PATCH v3 1/3] " Charlie Jenkins
@ 2025-01-07 4:07 ` Charlie Jenkins
2025-01-07 4:07 ` [PATCH v3 3/3] libperf: Add perf_evsel__refresh() function Charlie Jenkins
2 siblings, 0 replies; 6+ messages in thread
From: Charlie Jenkins @ 2025-01-07 4:07 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim, Mark Rutland, Alexander Shishkin, Jiri Olsa,
Ian Rogers, Adrian Hunter, Atish Patra
Cc: linux-perf-users, linux-kernel, Charlie Jenkins
Introduce PERF_EVENT_IOC_INC_EVENT_LIMIT and explain the differences
between it and PERF_EVENT_IOC_REFRESH.
Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
tools/perf/design.txt | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/tools/perf/design.txt b/tools/perf/design.txt
index aa8cfeabb7432d4011005f34a981fa3381caab09..1626ae83785a5773c255cc5219c2e9e0525dda19 100644
--- a/tools/perf/design.txt
+++ b/tools/perf/design.txt
@@ -439,6 +439,11 @@ Additionally, non-inherited overflow counters can use
to enable a counter for 'nr' events, after which it gets disabled again.
+PERF_EVENT_IOC_REFRESH will increment the event limit by 'nr' and enable the
+event. To increment the event limit without enabling it, use the following:
+
+ ioctl(fd, PERF_EVENT_IOC_INC_EVENT_LIMIT, nr);
+
A process can enable or disable all the counter groups that are
attached to it, using prctl:
--
2.34.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v3 3/3] libperf: Add perf_evsel__refresh() function
2025-01-07 4:07 [PATCH v3 0/3] perf: Add PERF_EVENT_IOC_INC_EVENT_LIMIT Charlie Jenkins
2025-01-07 4:07 ` [PATCH v3 1/3] " Charlie Jenkins
2025-01-07 4:07 ` [PATCH v3 2/3] perf: Document PERF_EVENT_IOC_INC_EVENT_LIMIT Charlie Jenkins
@ 2025-01-07 4:07 ` Charlie Jenkins
2 siblings, 0 replies; 6+ messages in thread
From: Charlie Jenkins @ 2025-01-07 4:07 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim, Mark Rutland, Alexander Shishkin, Jiri Olsa,
Ian Rogers, Adrian Hunter, Atish Patra
Cc: linux-perf-users, linux-kernel, Charlie Jenkins,
Shunsuke Nakamura
Introduce perf_evsel__refresh() to increment the overflow limit. Can
optionally enable the event immediately.
Co-developed-by: Shunsuke Nakamura <nakamura.shun@fujitsu.com>
Signed-off-by: Shunsuke Nakamura <nakamura.shun@fujitsu.com>
Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
tools/lib/perf/Documentation/libperf.txt | 2 ++
tools/lib/perf/evsel.c | 49 ++++++++++++++++++++++++++------
tools/lib/perf/include/perf/evsel.h | 2 ++
tools/lib/perf/libperf.map | 2 ++
4 files changed, 47 insertions(+), 8 deletions(-)
diff --git a/tools/lib/perf/Documentation/libperf.txt b/tools/lib/perf/Documentation/libperf.txt
index 59aabdd3cabff19c9a4835d9d20a74c6087d9a06..d557cb0279853c82dfc65533ba230255fced64bc 100644
--- a/tools/lib/perf/Documentation/libperf.txt
+++ b/tools/lib/perf/Documentation/libperf.txt
@@ -146,6 +146,8 @@ SYNOPSIS
int perf_evsel__enable_cpu(struct perf_evsel *evsel, int cpu_map_idx);
int perf_evsel__disable(struct perf_evsel *evsel);
int perf_evsel__disable_cpu(struct perf_evsel *evsel, int cpu_map_idx);
+ int perf_evsel__refresh(struct perf_evsel *evsel, int refresh, bool enable);
+ int perf_evsel__period(struct perf_evsel *evsel, uint64_t period);
struct perf_cpu_map *perf_evsel__cpus(struct perf_evsel *evsel);
struct perf_thread_map *perf_evsel__threads(struct perf_evsel *evsel);
struct perf_event_attr *perf_evsel__attr(struct perf_evsel *evsel);
diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
index c475319e2e410d31d072d81afb9e6277b16ef1f1..92633d426c9439afd7a8cde70dde8320d6a2efa3 100644
--- a/tools/lib/perf/evsel.c
+++ b/tools/lib/perf/evsel.c
@@ -19,6 +19,7 @@
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <asm/bug.h>
+#include "internal.h"
void perf_evsel__init(struct perf_evsel *evsel, struct perf_event_attr *attr,
int idx)
@@ -414,7 +415,7 @@ int perf_evsel__read(struct perf_evsel *evsel, int cpu_map_idx, int thread,
return 0;
}
-static int perf_evsel__ioctl(struct perf_evsel *evsel, int ioc, void *arg,
+static int perf_evsel__ioctl(struct perf_evsel *evsel, int ioc, unsigned long arg,
int cpu_map_idx, int thread)
{
int *fd = FD(evsel, cpu_map_idx, thread);
@@ -426,7 +427,7 @@ static int perf_evsel__ioctl(struct perf_evsel *evsel, int ioc, void *arg,
}
static int perf_evsel__run_ioctl(struct perf_evsel *evsel,
- int ioc, void *arg,
+ int ioc, unsigned long arg,
int cpu_map_idx)
{
int thread;
@@ -443,7 +444,7 @@ static int perf_evsel__run_ioctl(struct perf_evsel *evsel,
int perf_evsel__enable_cpu(struct perf_evsel *evsel, int cpu_map_idx)
{
- return perf_evsel__run_ioctl(evsel, PERF_EVENT_IOC_ENABLE, NULL, cpu_map_idx);
+ return perf_evsel__run_ioctl(evsel, PERF_EVENT_IOC_ENABLE, 0, cpu_map_idx);
}
int perf_evsel__enable_thread(struct perf_evsel *evsel, int thread)
@@ -453,7 +454,7 @@ int perf_evsel__enable_thread(struct perf_evsel *evsel, int thread)
int err;
perf_cpu_map__for_each_cpu(cpu, idx, evsel->cpus) {
- err = perf_evsel__ioctl(evsel, PERF_EVENT_IOC_ENABLE, NULL, idx, thread);
+ err = perf_evsel__ioctl(evsel, PERF_EVENT_IOC_ENABLE, 0, idx, thread);
if (err)
return err;
}
@@ -467,13 +468,13 @@ int perf_evsel__enable(struct perf_evsel *evsel)
int err = 0;
for (i = 0; i < xyarray__max_x(evsel->fd) && !err; i++)
- err = perf_evsel__run_ioctl(evsel, PERF_EVENT_IOC_ENABLE, NULL, i);
+ err = perf_evsel__run_ioctl(evsel, PERF_EVENT_IOC_ENABLE, 0, i);
return err;
}
int perf_evsel__disable_cpu(struct perf_evsel *evsel, int cpu_map_idx)
{
- return perf_evsel__run_ioctl(evsel, PERF_EVENT_IOC_DISABLE, NULL, cpu_map_idx);
+ return perf_evsel__run_ioctl(evsel, PERF_EVENT_IOC_DISABLE, 0, cpu_map_idx);
}
int perf_evsel__disable(struct perf_evsel *evsel)
@@ -482,7 +483,39 @@ int perf_evsel__disable(struct perf_evsel *evsel)
int err = 0;
for (i = 0; i < xyarray__max_x(evsel->fd) && !err; i++)
- err = perf_evsel__run_ioctl(evsel, PERF_EVENT_IOC_DISABLE, NULL, i);
+ err = perf_evsel__run_ioctl(evsel, PERF_EVENT_IOC_DISABLE, 0, i);
+ return err;
+}
+
+int perf_evsel__refresh(struct perf_evsel *evsel, int refresh, bool enable)
+{
+ int i, ioc;
+ int err = 0;
+
+ ioc = enable ? PERF_EVENT_IOC_REFRESH : PERF_EVENT_IOC_INC_EVENT_LIMIT;
+
+ for (i = 0; i < xyarray__max_x(evsel->fd) && !err; i++)
+ err = perf_evsel__run_ioctl(evsel, ioc, refresh, i);
+ return err;
+}
+
+int perf_evsel__period(struct perf_evsel *evsel, uint64_t period)
+{
+ struct perf_event_attr *attr;
+ int i;
+ int err = 0;
+
+ attr = perf_evsel__attr(evsel);
+
+ for (i = 0; i < xyarray__max_x(evsel->fd); i++) {
+ err = perf_evsel__run_ioctl(evsel, PERF_EVENT_IOC_PERIOD,
+ (unsigned long)&period, i);
+ if (err)
+ return err;
+ }
+
+ attr->sample_period = period;
+
return err;
}
@@ -493,7 +526,7 @@ int perf_evsel__apply_filter(struct perf_evsel *evsel, const char *filter)
for (i = 0; i < perf_cpu_map__nr(evsel->cpus) && !err; i++)
err = perf_evsel__run_ioctl(evsel,
PERF_EVENT_IOC_SET_FILTER,
- (void *)filter, i);
+ (unsigned long)filter, i);
return err;
}
diff --git a/tools/lib/perf/include/perf/evsel.h b/tools/lib/perf/include/perf/evsel.h
index 6f92204075c244bc623b26dc2c97fa4c835a4228..19d30bab8fe1e2d860b432855bc01958ba5e54c8 100644
--- a/tools/lib/perf/include/perf/evsel.h
+++ b/tools/lib/perf/include/perf/evsel.h
@@ -40,6 +40,8 @@ LIBPERF_API int perf_evsel__enable(struct perf_evsel *evsel);
LIBPERF_API int perf_evsel__enable_cpu(struct perf_evsel *evsel, int cpu_map_idx);
LIBPERF_API int perf_evsel__enable_thread(struct perf_evsel *evsel, int thread);
LIBPERF_API int perf_evsel__disable(struct perf_evsel *evsel);
+LIBPERF_API int perf_evsel__refresh(struct perf_evsel *evsel, int refresh, bool enable);
+LIBPERF_API int perf_evsel__period(struct perf_evsel *evsel, uint64_t period);
LIBPERF_API int perf_evsel__disable_cpu(struct perf_evsel *evsel, int cpu_map_idx);
LIBPERF_API struct perf_cpu_map *perf_evsel__cpus(struct perf_evsel *evsel);
LIBPERF_API struct perf_thread_map *perf_evsel__threads(struct perf_evsel *evsel);
diff --git a/tools/lib/perf/libperf.map b/tools/lib/perf/libperf.map
index fdd8304fe9d05862376c122d68777a6bf6a03d80..d67299bd5216b02e09a47a1b1ef947eef460cf17 100644
--- a/tools/lib/perf/libperf.map
+++ b/tools/lib/perf/libperf.map
@@ -33,6 +33,8 @@ LIBPERF_0.0.1 {
perf_evsel__munmap;
perf_evsel__mmap_base;
perf_evsel__read;
+ perf_evsel__refresh;
+ perf_evsel__period;
perf_evsel__cpus;
perf_evsel__threads;
perf_evsel__attr;
--
2.34.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v3 1/3] perf: Add PERF_EVENT_IOC_INC_EVENT_LIMIT
2025-01-07 4:07 ` [PATCH v3 1/3] " Charlie Jenkins
@ 2025-01-13 13:18 ` Peter Zijlstra
2025-01-13 18:59 ` Charlie Jenkins
0 siblings, 1 reply; 6+ messages in thread
From: Peter Zijlstra @ 2025-01-13 13:18 UTC (permalink / raw)
To: Charlie Jenkins
Cc: Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, Mark Rutland,
Alexander Shishkin, Jiri Olsa, Ian Rogers, Adrian Hunter,
Atish Patra, linux-perf-users, linux-kernel
On Mon, Jan 06, 2025 at 08:07:32PM -0800, Charlie Jenkins wrote:
> PERF_EVENT_IOC_REFRESH immediately enables after incrementing
> event_limit. Provide a new ioctl flag that allows programs to increment
> event_limit without enabling the event. A usecase for this is to set an
> event_limit in combination with enable_on_exec.
Utter lack of WHY.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v3 1/3] perf: Add PERF_EVENT_IOC_INC_EVENT_LIMIT
2025-01-13 13:18 ` Peter Zijlstra
@ 2025-01-13 18:59 ` Charlie Jenkins
0 siblings, 0 replies; 6+ messages in thread
From: Charlie Jenkins @ 2025-01-13 18:59 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, Mark Rutland,
Alexander Shishkin, Jiri Olsa, Ian Rogers, Adrian Hunter,
Atish Patra, linux-perf-users, linux-kernel
On Mon, Jan 13, 2025 at 02:18:12PM +0100, Peter Zijlstra wrote:
> On Mon, Jan 06, 2025 at 08:07:32PM -0800, Charlie Jenkins wrote:
> > PERF_EVENT_IOC_REFRESH immediately enables after incrementing
> > event_limit. Provide a new ioctl flag that allows programs to increment
> > event_limit without enabling the event. A usecase for this is to set an
> > event_limit in combination with enable_on_exec.
>
>
> Utter lack of WHY.
My usecase is being able to use libperf to calculate performance metrics
from running a program for X number of instructions.
PERF_EVENT_IOC_REFRESH can be used to stop the counters after the
instruction sampling threshold has been hit. This requires being able to
start PERF_EVENT_IOC_REFRESH as soon as the program starts executing,
which is a perfect application for enable_on_exec.
- Charlie
^ permalink raw reply [flat|nested] 6+ messages in thread
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2025-01-07 4:07 [PATCH v3 0/3] perf: Add PERF_EVENT_IOC_INC_EVENT_LIMIT Charlie Jenkins
2025-01-07 4:07 ` [PATCH v3 1/3] " Charlie Jenkins
2025-01-13 13:18 ` Peter Zijlstra
2025-01-13 18:59 ` Charlie Jenkins
2025-01-07 4:07 ` [PATCH v3 2/3] perf: Document PERF_EVENT_IOC_INC_EVENT_LIMIT Charlie Jenkins
2025-01-07 4:07 ` [PATCH v3 3/3] libperf: Add perf_evsel__refresh() function Charlie Jenkins
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