perf: Rework the PMU methods

Replace pmu::{enable,disable,start,stop,unthrottle} with
pmu::{add,del,start,stop}, all of which take a flags argument.

The new interface extends the capability to stop a counter while
keeping it scheduled on the PMU. We replace the throttled state with
the generic stopped state.

This also allows us to efficiently stop/start counters over certain
code paths (like IRQ handlers).

It also allows scheduling a counter without it starting, allowing for
a generic frozen state (useful for rotating stopped counters).

The stopped state is implemented in two different ways, depending on
how the architecture implemented the throttled state:

 1) We disable the counter:
    a) the pmu has per-counter enable bits, we flip that
    b) we program a NOP event, preserving the counter state

 2) We store the counter state and ignore all read/overflow events

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: paulus <paulus@samba.org>
Cc: stephane eranian <eranian@googlemail.com>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Lin Ming <ming.m.lin@intel.com>
Cc: Yanmin <yanmin_zhang@linux.intel.com>
Cc: Deng-Cheng Zhu <dengcheng.zhu@gmail.com>
Cc: David Miller <davem@davemloft.net>
Cc: Michael Cree <mcree@orcon.net.nz>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 67 insertions, 42 deletions

diff --git a/arch/sparc/kernel/perf_event.c b/arch/sparc/kernel/perf_event.c
index 37cae676536c..516be2314b54 100644
--- a/arch/sparc/kernel/perf_event.c
+++ b/arch/sparc/kernel/perf_event.c
@@ -658,13 +658,16 @@ static u64 maybe_change_configuration(struct cpu_hw_events *cpuc, u64 pcr)
 
                 enc = perf_event_get_enc(cpuc->events[i]);
                 pcr &= ~mask_for_index(idx);
-                pcr |= event_encoding(enc, idx);
+                if (hwc->state & PERF_HES_STOPPED)
+                        pcr |= nop_for_index(idx);
+                else
+                        pcr |= event_encoding(enc, idx);
         }
 out:
         return pcr;
 }
 
-static void sparc_pmu_pmu_enable(struct pmu *pmu)
+static void sparc_pmu_enable(struct pmu *pmu)
 {
         struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
         u64 pcr;
@@ -691,7 +694,7 @@ static void sparc_pmu_pmu_enable(struct pmu *pmu)
         pcr_ops->write(cpuc->pcr);
 }
 
-static void sparc_pmu_pmu_disable(struct pmu *pmu)
+static void sparc_pmu_disable(struct pmu *pmu)
 {
         struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
         u64 val;
@@ -710,10 +713,53 @@ static void sparc_pmu_pmu_disable(struct pmu *pmu)
         pcr_ops->write(cpuc->pcr);
 }
 
-static void sparc_pmu_disable(struct perf_event *event)
+static int active_event_index(struct cpu_hw_events *cpuc,
+                              struct perf_event *event)
+{
+        int i;
+
+        for (i = 0; i < cpuc->n_events; i++) {
+                if (cpuc->event[i] == event)
+                        break;
+        }
+        BUG_ON(i == cpuc->n_events);
+        return cpuc->current_idx[i];
+}
+
+static void sparc_pmu_start(struct perf_event *event, int flags)
+{
+        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
+        int idx = active_event_index(cpuc, event);
+
+        if (flags & PERF_EF_RELOAD) {
+                WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE));
+                sparc_perf_event_set_period(event, &event->hw, idx);
+        }
+
+        event->hw.state = 0;
+
+        sparc_pmu_enable_event(cpuc, &event->hw, idx);
+}
+
+static void sparc_pmu_stop(struct perf_event *event, int flags)
+{
+        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
+        int idx = active_event_index(cpuc, event);
+
+        if (!(event->hw.state & PERF_HES_STOPPED)) {
+                sparc_pmu_disable_event(cpuc, &event->hw, idx);
+                event->hw.state |= PERF_HES_STOPPED;
+        }
+
+        if (!(event->hw.state & PERF_HES_UPTODATE) && (flags & PERF_EF_UPDATE)) {
+                sparc_perf_event_update(event, &event->hw, idx);
+                event->hw.state |= PERF_HES_UPTODATE;
+        }
+}
+
+static void sparc_pmu_del(struct perf_event *event, int _flags)
 {
         struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
-        struct hw_perf_event *hwc = &event->hw;
         unsigned long flags;
         int i;
 
@@ -722,7 +768,10 @@ static void sparc_pmu_disable(struct perf_event *event)
 
         for (i = 0; i < cpuc->n_events; i++) {
                 if (event == cpuc->event[i]) {
-                        int idx = cpuc->current_idx[i];
+                        /* Absorb the final count and turn off the
+                         * event.
+                         */
+                        sparc_pmu_stop(event, PERF_EF_UPDATE);
 
                         /* Shift remaining entries down into
                          * the existing slot.
@@ -734,13 +783,6 @@ static void sparc_pmu_disable(struct perf_event *event)
                                         cpuc->current_idx[i];
                         }
 
-                        /* Absorb the final count and turn off the
-                         * event.
-                         */
-                        sparc_pmu_disable_event(cpuc, hwc, idx);
-                        barrier();
-                        sparc_perf_event_update(event, hwc, idx);
-
                         perf_event_update_userpage(event);
 
                         cpuc->n_events--;
@@ -752,19 +794,6 @@ static void sparc_pmu_disable(struct perf_event *event)
         local_irq_restore(flags);
 }
 
-static int active_event_index(struct cpu_hw_events *cpuc,
-                              struct perf_event *event)
-{
-        int i;
-
-        for (i = 0; i < cpuc->n_events; i++) {
-                if (cpuc->event[i] == event)
-                        break;
-        }
-        BUG_ON(i == cpuc->n_events);
-        return cpuc->current_idx[i];
-}
-
 static void sparc_pmu_read(struct perf_event *event)
 {
         struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
@@ -774,15 +803,6 @@ static void sparc_pmu_read(struct perf_event *event)
         sparc_perf_event_update(event, hwc, idx);
 }
 
-static void sparc_pmu_unthrottle(struct perf_event *event)
-{
-        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
-        int idx = active_event_index(cpuc, event);
-        struct hw_perf_event *hwc = &event->hw;
-
-        sparc_pmu_enable_event(cpuc, hwc, idx);
-}
-
 static atomic_t active_events = ATOMIC_INIT(0);
 static DEFINE_MUTEX(pmc_grab_mutex);
 
@@ -984,7 +1004,7 @@ static int collect_events(struct perf_event *group, int max_count,
         return n;
 }
 
-static int sparc_pmu_enable(struct perf_event *event)
+static int sparc_pmu_add(struct perf_event *event, int ef_flags)
 {
         struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
         int n0, ret = -EAGAIN;
@@ -1001,6 +1021,10 @@ static int sparc_pmu_enable(struct perf_event *event)
         cpuc->events[n0] = event->hw.event_base;
         cpuc->current_idx[n0] = PIC_NO_INDEX;
 
+        event->hw.state = PERF_HES_UPTODATE;
+        if (!(ef_flags & PERF_EF_START))
+                event->hw.state |= PERF_HES_STOPPED;
+
         /*
          * If group events scheduling transaction was started,
          * skip the schedulability test here, it will be peformed
@@ -1156,13 +1180,14 @@ static int sparc_pmu_commit_txn(struct pmu *pmu)
 }
 
 static struct pmu pmu = {
-        .pmu_enable     = sparc_pmu_pmu_enable,
-        .pmu_disable    = sparc_pmu_pmu_disable,
+        .pmu_enable     = sparc_pmu_enable,
+        .pmu_disable    = sparc_pmu_disable,
         .event_init     = sparc_pmu_event_init,
-        .enable         = sparc_pmu_enable,
-        .disable        = sparc_pmu_disable,
+        .add            = sparc_pmu_add,
+        .del            = sparc_pmu_del,
+        .start          = sparc_pmu_start,
+        .stop           = sparc_pmu_stop,
         .read           = sparc_pmu_read,
-        .unthrottle     = sparc_pmu_unthrottle,
         .start_txn      = sparc_pmu_start_txn,
         .cancel_txn     = sparc_pmu_cancel_txn,
         .commit_txn     = sparc_pmu_commit_txn,
@@ -1243,7 +1268,7 @@ static int __kprobes perf_event_nmi_handler(struct notifier_block *self,
                         continue;
 
                 if (perf_event_overflow(event, 1, &data, regs))
-                        sparc_pmu_disable_event(cpuc, hwc, idx);
+                        sparc_pmu_stop(event, 0);
         }
 
         return NOTIFY_STOP;