lkml.org 
[lkml]   [2021]   [Dec]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH v3] perf/core: Set event shadow time for inactive events too
On Mon, Dec 20, 2021 at 10:30:34AM +0100, Peter Zijlstra wrote:

> Ohh.. argh. I think I see why, it looses the context time enable edge,
> and because this is all strictly per-event in the uapi (there is no ctx
> representation) it can't be cured by improving ctx time handling :/
>
> Bah, I so hate this.
>

I wonder... could we get away with something like this...


---
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2722,13 +2722,17 @@ void arch_perf_update_userpage(struct pe
struct cyc2ns_data data;
u64 offset;

- userpg->cap_user_time = 0;
- userpg->cap_user_time_zero = 0;
- userpg->cap_user_rdpmc =
- !!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED);
+ userpg->cap_user_rdpmc = !!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED);
userpg->pmc_width = x86_pmu.cntval_bits;

- if (!using_native_sched_clock() || !sched_clock_stable())
+ if (unlikely(!using_native_sched_clock() || !sched_clock_stable())) {
+ userpg->cap_user_time = 0;
+ userpg->cap_user_time_zero = 0;
+ return;
+ }
+
+ /* already set the time fields before */
+ if (likely(userpf->cap_user_time))
return;

cyc2ns_read_begin(&data);
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -612,6 +612,7 @@ struct swevent_hlist {
#define PERF_ATTACH_ITRACE 0x10
#define PERF_ATTACH_SCHED_CB 0x20
#define PERF_ATTACH_CHILD 0x40
+#define PERF_ATTACH_SELF 0x80

struct perf_cgroup;
struct perf_buffer;
@@ -812,6 +813,7 @@ struct perf_event_context {

int nr_events;
int nr_active;
+ int nr_self;
int is_active;
int nr_stat;
int nr_freq;
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1877,6 +1877,8 @@ list_add_event(struct perf_event *event,
ctx->nr_events++;
if (event->attr.inherit_stat)
ctx->nr_stat++;
+ if (event->attach_state & PERF_ATTACH_SELF)
+ ctx->nr_self++;

if (event->state > PERF_EVENT_STATE_OFF)
perf_cgroup_event_enable(event, ctx);
@@ -2068,6 +2070,8 @@ list_del_event(struct perf_event *event,
ctx->nr_events--;
if (event->attr.inherit_stat)
ctx->nr_stat--;
+ if (event->attach_state & PERF_ATTACH_SELF)
+ ctx->nr_self--;

list_del_rcu(&event->event_entry);

@@ -3755,7 +3759,8 @@ static noinline int visit_groups_merge(s
*/
static inline bool event_update_userpage(struct perf_event *event)
{
- if (likely(!atomic_read(&event->mmap_count)))
+ if (likely(!atomic_read(&event->mmap_count) ||
+ !(event->attach_state & PERF_ATTACH_SELF)))
return false;

perf_event_update_time(event);
@@ -3800,7 +3805,8 @@ static int merge_sched_in(struct perf_ev
} else {
ctx->rotate_necessary = 1;
perf_mux_hrtimer_restart(cpuctx);
- group_update_userpage(event);
+ if (ctx->nr_self)
+ group_update_userpage(event);
}
}

@@ -5900,6 +5906,9 @@ void perf_event_update_userpage(struct p
if (!rb)
goto unlock;

+ if (!(event->attach_state & PERF_ATTACH_SELF))
+ goto unlock;
+
/*
* compute total_time_enabled, total_time_running
* based on snapshot values taken when the event
@@ -11613,6 +11622,8 @@ perf_event_alloc(struct perf_event_attr
* pmu before we get a ctx.
*/
event->hw.target = get_task_struct(task);
+ if (event->hw.target == current && !attr->inherit)
+ event->attach_state |= PERF_ATTACH_SELF;
}

event->clock = &local_clock;
\
 
 \ /
  Last update: 2021-12-21 13:40    [W:0.053 / U:5.128 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site