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authorPeter Zijlstra <peterz@infradead.org>2015-04-17 20:05:30 +0200
committerIngo Molnar <mingo@kernel.org>2015-05-08 12:25:38 +0200
commitff303e66c240ba6269e31817a386995440a18c99 (patch)
treeaa4e506beabc409966d9cda0c722dee41e8d8ce9 /include/linux/perf_event.h
parent1836ac856e4fb446e48afa4f8cae897d4856b06c (diff)
downloadop-kernel-dev-ff303e66c240ba6269e31817a386995440a18c99.zip
op-kernel-dev-ff303e66c240ba6269e31817a386995440a18c99.tar.gz
perf: Fix software migrate events
Stephane asked about PERF_COUNT_SW_CPU_MIGRATIONS and I realized it was borken: > The problem is that the task isn't actually scheduled while its being > migrated (obviously), and if its not scheduled, the counters aren't > scheduled either, so there's no observing of the fact. > > A further problem with migrations is that many migrations happen from > softirq context, which is nested inside the 'random' task context of > whoemever happens to run at that time, similarly for the wakeup > migrations triggered from (soft)irq context. All those end up being > accounted in the task that's currently running, eg. your 'ls'. The below cures this by marking a task as migrated and accounting it on the subsequent sched_in(). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/perf_event.h')
-rw-r--r--include/linux/perf_event.h24
1 files changed, 24 insertions, 0 deletions
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 61992cf..e86f85a 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -798,11 +798,33 @@ perf_sw_event_sched(u32 event_id, u64 nr, u64 addr)
extern struct static_key_deferred perf_sched_events;
+static __always_inline bool
+perf_sw_migrate_enabled(void)
+{
+ if (static_key_false(&perf_swevent_enabled[PERF_COUNT_SW_CPU_MIGRATIONS]))
+ return true;
+ return false;
+}
+
+static inline void perf_event_task_migrate(struct task_struct *task)
+{
+ if (perf_sw_migrate_enabled())
+ task->sched_migrated = 1;
+}
+
static inline void perf_event_task_sched_in(struct task_struct *prev,
struct task_struct *task)
{
if (static_key_false(&perf_sched_events.key))
__perf_event_task_sched_in(prev, task);
+
+ if (perf_sw_migrate_enabled() && task->sched_migrated) {
+ struct pt_regs *regs = this_cpu_ptr(&__perf_regs[0]);
+
+ perf_fetch_caller_regs(regs);
+ ___perf_sw_event(PERF_COUNT_SW_CPU_MIGRATIONS, 1, regs, 0);
+ task->sched_migrated = 0;
+ }
}
static inline void perf_event_task_sched_out(struct task_struct *prev,
@@ -925,6 +947,8 @@ perf_aux_output_skip(struct perf_output_handle *handle,
static inline void *
perf_get_aux(struct perf_output_handle *handle) { return NULL; }
static inline void
+perf_event_task_migrate(struct task_struct *task) { }
+static inline void
perf_event_task_sched_in(struct task_struct *prev,
struct task_struct *task) { }
static inline void
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