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Subject[PATCH 2/3] perf-events: Add support for supplementary event registers v4
Date
From: Andi Kleen <ak@linux.intel.com>

Intel Nehalem/Westmere have a special OFFCORE_RESPONSE event
that can be used to monitor any offcore accesses from a core.
This is a very useful event for various tunings, and it's
also needed to implement the generic LLC-* events correctly.

Unfortunately this event requires programming a mask in a separate
register. And worse this separate register is per core, not per
CPU thread.

This patch adds:
- Teaches perf_events that OFFCORE_RESPONSE needs extra parameters.
The extra parameters are passed by user space in the unused upper
32bits of the config word.
- Add support to the Intel perf_event core to schedule per
core resources. This adds fairly generic infrastructure that
can be also used for other per core resources.
The basic code has is patterned after the similar AMD northbridge
constraints code.

Thanks to Stephane Eranian who pointed out some problems
in the original version and suggested improvements.

Cc: eranian@google.com
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
arch/x86/kernel/cpu/perf_event.c | 70 +++++++++++
arch/x86/kernel/cpu/perf_event_intel.c | 198 ++++++++++++++++++++++++++++++++
include/linux/perf_event.h | 2 +
3 files changed, 270 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 817d2b1..a6754ea 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -93,6 +93,8 @@ struct amd_nb {
struct event_constraint event_constraints[X86_PMC_IDX_MAX];
};

+struct intel_percore;
+
#define MAX_LBR_ENTRIES 16

struct cpu_hw_events {
@@ -128,6 +130,13 @@ struct cpu_hw_events {
struct perf_branch_entry lbr_entries[MAX_LBR_ENTRIES];

/*
+ * Intel percore register state.
+ * Coordinate shared resources between HT threads.
+ */
+ int percore_used; /* Used by this CPU? */
+ struct intel_percore *per_core;
+
+ /*
* AMD specific bits
*/
struct amd_nb *amd_nb;
@@ -175,6 +184,32 @@ struct cpu_hw_events {
#define for_each_event_constraint(e, c) \
for ((e) = (c); (e)->weight; (e)++)

+/*
+ * Extra registers for specific events.
+ * Some events need large masks and require external MSRs.
+ * Define a mapping to these extra registers.
+ * The actual contents are still encoded in unused parts of the
+ * original config u64.
+ */
+struct extra_reg {
+ unsigned int event;
+ unsigned int msr;
+ unsigned int extra_shift;
+ u64 config_mask;
+ u64 valid_mask;
+};
+
+#define EVENT_EXTRA_REG(e, ms, m, vm, es) { \
+ .event = (e), \
+ .msr = (ms), \
+ .config_mask = (m), \
+ .valid_mask = (vm), \
+ .extra_shift = (es), \
+ }
+#define INTEL_EVENT_EXTRA_REG(event, msr, vm, es) \
+ EVENT_EXTRA_REG(event, msr, ARCH_PERFMON_EVENTSEL_EVENT, vm, es)
+#define EVENT_EXTRA_END EVENT_EXTRA_REG(0, 0, 0, 0, 0)
+
union perf_capabilities {
struct {
u64 lbr_format : 6;
@@ -219,6 +254,7 @@ struct x86_pmu {
void (*put_event_constraints)(struct cpu_hw_events *cpuc,
struct perf_event *event);
struct event_constraint *event_constraints;
+ struct event_constraint *percore_constraints;
void (*quirks)(void);
int perfctr_second_write;

@@ -247,6 +283,11 @@ struct x86_pmu {
*/
unsigned long lbr_tos, lbr_from, lbr_to; /* MSR base regs */
int lbr_nr; /* hardware stack size */
+
+ /*
+ * Extra registers for events
+ */
+ struct extra_reg *extra_regs;
};

static struct x86_pmu x86_pmu __read_mostly;
@@ -321,6 +362,33 @@ again:
return new_raw_count;
}

+/*
+ * Find and validate any extra registers to set up.
+ */
+static int x86_pmu_extra_regs(u64 config, struct perf_event *event)
+{
+ struct extra_reg *er;
+ u64 extra;
+
+ event->hw.extra_reg = 0;
+ event->hw.extra_config = 0;
+
+ if (!x86_pmu.extra_regs)
+ return 0;
+
+ for (er = x86_pmu.extra_regs; er->msr; er++) {
+ if (er->event != (config & er->config_mask))
+ continue;
+ event->hw.extra_reg = er->msr;
+ extra = config >> er->extra_shift;
+ if (extra & ~er->valid_mask)
+ return -EINVAL;
+ event->hw.extra_config = extra;
+ break;
+ }
+ return 0;
+}
+
static atomic_t active_events;
static DEFINE_MUTEX(pmc_reserve_mutex);

@@ -880,6 +948,8 @@ static void x86_pmu_enable(struct pmu *pmu)
static inline void __x86_pmu_enable_event(struct hw_perf_event *hwc,
u64 enable_mask)
{
+ if (hwc->extra_reg)
+ wrmsrl(hwc->extra_reg, hwc->extra_config);
wrmsrl(hwc->config_base + hwc->idx, hwc->config | enable_mask);
}

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index c8f5c08..04fdcf9 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1,5 +1,27 @@
#ifdef CONFIG_CPU_SUP_INTEL

+#define MAX_EXTRA_REGS 2
+
+/*
+ * Per register state.
+ */
+struct er_account {
+ int ref; /* reference count */
+ unsigned int extra_reg; /* extra MSR number */
+ u64 extra_config; /* extra MSR config */
+};
+
+/*
+ * Per core state
+ * This used to coordinate shared registers for HT threads.
+ */
+struct intel_percore {
+ raw_spinlock_t lock; /* protect structure */
+ struct er_account regs[MAX_EXTRA_REGS];
+ int refcnt; /* number of threads */
+ unsigned core_id;
+};
+
/*
* Intel PerfMon, used on Core and later.
*/
@@ -64,6 +86,18 @@ static struct event_constraint intel_nehalem_event_constraints[] =
EVENT_CONSTRAINT_END
};

+static struct extra_reg intel_nehalem_extra_regs[] =
+{
+ INTEL_EVENT_EXTRA_REG(0xb7, 0x1a6, 0xffff, 32), /* OFFCORE_RESPONSE_0 */
+ EVENT_EXTRA_END
+};
+
+static struct event_constraint intel_nehalem_percore_constraints[] =
+{
+ INTEL_EVENT_CONSTRAINT(0xb7, 0),
+ EVENT_CONSTRAINT_END
+};
+
static struct event_constraint intel_westmere_event_constraints[] =
{
FIXED_EVENT_CONSTRAINT(0x00c0, 0), /* INST_RETIRED.ANY */
@@ -76,6 +110,20 @@ static struct event_constraint intel_westmere_event_constraints[] =
EVENT_CONSTRAINT_END
};

+static struct extra_reg intel_westmere_extra_regs[] =
+{
+ INTEL_EVENT_EXTRA_REG(0xb7, 0x1a6, 0xffff, 32), /* OFFCORE_RESPONSE_0 */
+ INTEL_EVENT_EXTRA_REG(0xbb, 0x1a7, 0xffff, 32), /* OFFCORE_RESPONSE_1 */
+ EVENT_EXTRA_END
+};
+
+static struct event_constraint intel_westmere_percore_constraints[] =
+{
+ INTEL_EVENT_CONSTRAINT(0xb7, 0),
+ INTEL_EVENT_CONSTRAINT(0xbb, 0),
+ EVENT_CONSTRAINT_END
+};
+
static struct event_constraint intel_gen_event_constraints[] =
{
FIXED_EVENT_CONSTRAINT(0x00c0, 0), /* INST_RETIRED.ANY */
@@ -794,6 +842,66 @@ intel_bts_constraints(struct perf_event *event)
}

static struct event_constraint *
+intel_percore_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
+{
+ struct hw_perf_event *hwc = &event->hw;
+ unsigned int e = hwc->config & ARCH_PERFMON_EVENTSEL_EVENT;
+ struct event_constraint *c;
+ struct intel_percore *pc;
+ struct er_account *era;
+ int i;
+ int free_slot;
+ int found;
+
+ if (!x86_pmu.percore_constraints)
+ return NULL;
+
+ for (c = x86_pmu.percore_constraints; c->cmask; c++) {
+ if (e != c->code)
+ continue;
+
+ /*
+ * Allocate resource per core.
+ */
+ c = NULL;
+ pc = cpuc->per_core;
+ if (!pc)
+ break;
+ c = &emptyconstraint;
+ raw_spin_lock(&pc->lock);
+ free_slot = -1;
+ found = 0;
+ for (i = 0; i < MAX_EXTRA_REGS; i++) {
+ era = &pc->regs[i];
+ if (era->ref > 0 && hwc->extra_reg == era->extra_reg) {
+ /* Allow sharing same config */
+ if (hwc->extra_config == era->extra_config) {
+ era->ref++;
+ cpuc->percore_used = 1;
+ c = NULL;
+ }
+ /* else conflict */
+ found = 1;
+ break;
+ } else if (era->ref == 0 && free_slot == -1)
+ free_slot = i;
+ }
+ if (!found && free_slot != -1) {
+ era = &pc->regs[free_slot];
+ era->ref = 1;
+ era->extra_reg = hwc->extra_reg;
+ era->extra_config = hwc->extra_config;
+ cpuc->percore_used = 1;
+ c = NULL;
+ }
+ raw_spin_unlock(&pc->lock);
+ return c;
+ }
+
+ return NULL;
+}
+
+static struct event_constraint *
intel_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
{
struct event_constraint *c;
@@ -806,9 +914,50 @@ intel_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event
if (c)
return c;

+ c = intel_percore_constraints(cpuc, event);
+ if (c)
+ return c;
+
return x86_get_event_constraints(cpuc, event);
}

+static void intel_put_event_constraints(struct cpu_hw_events *cpuc,
+ struct perf_event *event)
+{
+ struct extra_reg *er;
+ struct intel_percore *pc;
+ struct er_account *era;
+ struct hw_perf_event *hwc = &event->hw;
+ int i, allref;
+
+ if (!cpuc->percore_used)
+ return;
+
+ for (er = x86_pmu.extra_regs; er->msr; er++) {
+ if (er->event != (hwc->config & er->config_mask))
+ continue;
+
+ pc = cpuc->per_core;
+ raw_spin_lock(&pc->lock);
+ for (i = 0; i < MAX_EXTRA_REGS; i++) {
+ era = &pc->regs[i];
+ if (era->ref > 0 &&
+ era->extra_config == hwc->extra_config &&
+ era->extra_reg == er->msr) {
+ era->ref--;
+ break;
+ }
+ }
+ allref = 0;
+ for (i = 0; i < MAX_EXTRA_REGS; i++)
+ allref += pc->regs[i].ref;
+ if (allref == 0)
+ cpuc->percore_used = 0;
+ raw_spin_unlock(&pc->lock);
+ break;
+ }
+}
+
static int intel_pmu_hw_config(struct perf_event *event)
{
int ret = x86_pmu_hw_config(event);
@@ -854,11 +1003,43 @@ static __initconst const struct x86_pmu core_pmu = {
*/
.max_period = (1ULL << 31) - 1,
.get_event_constraints = intel_get_event_constraints,
+ .put_event_constraints = intel_put_event_constraints,
.event_constraints = intel_core_event_constraints,
};

+static int intel_pmu_cpu_prepare(int cpu)
+{
+ struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
+
+ cpuc->per_core = kzalloc_node(sizeof(struct intel_percore),
+ GFP_KERNEL, cpu_to_node(cpu));
+ if (!cpuc->per_core)
+ return NOTIFY_BAD;
+
+ raw_spin_lock_init(&cpuc->per_core->lock);
+ cpuc->per_core->core_id = -1;
+ return NOTIFY_OK;
+}
+
static void intel_pmu_cpu_starting(int cpu)
{
+ struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
+ int core_id = topology_core_id(cpu);
+ int i;
+
+ for_each_online_cpu(i) {
+ struct intel_percore *pc = per_cpu(cpu_hw_events, i).per_core;
+
+ if (pc && pc->core_id == core_id) {
+ kfree(cpuc->per_core);
+ cpuc->per_core = pc;
+ break;
+ }
+ }
+
+ cpuc->per_core->core_id = core_id;
+ cpuc->per_core->refcnt++;
+
init_debug_store_on_cpu(cpu);
/*
* Deal with CPUs that don't clear their LBRs on power-up.
@@ -868,6 +1049,15 @@ static void intel_pmu_cpu_starting(int cpu)

static void intel_pmu_cpu_dying(int cpu)
{
+ struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
+ struct intel_percore *pc = cpuc->per_core;
+
+ if (pc) {
+ if (pc->core_id == -1 || --pc->refcnt == 0)
+ kfree(pc);
+ cpuc->per_core = NULL;
+ }
+
fini_debug_store_on_cpu(cpu);
}

@@ -892,7 +1082,9 @@ static __initconst const struct x86_pmu intel_pmu = {
*/
.max_period = (1ULL << 31) - 1,
.get_event_constraints = intel_get_event_constraints,
+ .put_event_constraints = intel_put_event_constraints,

+ .cpu_prepare = intel_pmu_cpu_prepare,
.cpu_starting = intel_pmu_cpu_starting,
.cpu_dying = intel_pmu_cpu_dying,
};
@@ -1010,7 +1202,10 @@ static __init int intel_pmu_init(void)
intel_pmu_lbr_init_nhm();

x86_pmu.event_constraints = intel_nehalem_event_constraints;
+ x86_pmu.percore_constraints =
+ intel_nehalem_percore_constraints;
x86_pmu.enable_all = intel_pmu_nhm_enable_all;
+ x86_pmu.extra_regs = intel_nehalem_extra_regs;
pr_cont("Nehalem events, ");
break;

@@ -1032,7 +1227,10 @@ static __init int intel_pmu_init(void)
intel_pmu_lbr_init_nhm();

x86_pmu.event_constraints = intel_westmere_event_constraints;
+ x86_pmu.percore_constraints =
+ intel_westmere_percore_constraints;
x86_pmu.enable_all = intel_pmu_nhm_enable_all;
+ x86_pmu.extra_regs = intel_westmere_extra_regs;
pr_cont("Westmere events, ");
break;

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index cbf04cc..7e3f231 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -529,6 +529,8 @@ struct hw_perf_event {
unsigned long event_base;
int idx;
int last_cpu;
+ unsigned int extra_reg;
+ u64 extra_config;
};
struct { /* software */
struct hrtimer hrtimer;
--
1.7.1


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