[PATCH V2 0/4] PEBS DS bug fix and optimization

[PATCH V2 0/4] PEBS DS bug fix and optimization

[kan.liang]

From: Kan Liang <kan.liang@linux.intel.com>

Changes since V1:
- Fix a PEBS DS bug which also impacts the existing implementation (new)
- Factor out generic functions for PEBS records processing (Peter)
- Update the description to explain the reason of moving
  intel_pmu_save_and_restart() related codes to the end and droping
  the return.

The V1 can be found at
https://lore.kernel.org/lkml/20241113151427.677169-1-kan.liang@linux.intel.com/

Kan Liang (4):
  perf/x86/intel/ds: Unconditionally drain PEBS DS when changing
    PEBS_DATA_CFG
  perf/x86/intel/ds: Clarify adaptive PEBS processing
  perf/x86/intel/ds: Factor out functions for PEBS records processing
  perf/x86/intel/ds: Simplify the PEBS records processing for adaptive
    PEBS

 arch/x86/events/intel/ds.c        | 191 ++++++++++++++++++------------
 arch/x86/include/asm/perf_event.h |  16 ++-
 2 files changed, 128 insertions(+), 79 deletions(-)

-- 
2.38.1

[PATCH V2 1/4] perf/x86/intel/ds: Unconditionally drain PEBS DS when changing PEBS_DATA_CFG

[kan.liang]

From: Kan Liang <kan.liang@linux.intel.com>

The PEBS kernel warnings can still be observed with the below case.

when the below commands are running in parallel for a while.

  while true;
  do
	perf record --no-buildid -a --intr-regs=AX  \
		    -e cpu/event=0xd0,umask=0x81/pp \
		    -c 10003 -o /dev/null ./triad;
  done &

  while true;
  do
	perf record -e 'cpu/mem-loads,ldlat=3/uP' -W -d -- ./dtlb
  done

The commit b752ea0c28e3 ("perf/x86/intel/ds: Flush PEBS DS when changing
PEBS_DATA_CFG") intends to flush the entire PEBS buffer before the
hardware is reprogrammed. However, it fails in the above case.

The first perf command utilizes the large PEBS, while the second perf
command only utilizes a single PEBS. When the second perf event is
added, only the n_pebs++. The intel_pmu_pebs_enable() is invoked after
intel_pmu_pebs_add(). So the cpuc->n_pebs == cpuc->n_large_pebs check in
the intel_pmu_drain_large_pebs() fails. The PEBS DS is not flushed.
The new PEBS event should not be taken into account when flushing the
existing PEBS DS.

The check is unnecessary here. Before the hardware is reprogrammed, all
the stale records must be drained unconditionally.

For single PEBS or PEBS-vi-pt, the DS must be empty. The drain_pebs()
can handle the empty case. There is no harm to unconditionally drain the
PEBS DS.

Fixes: b752ea0c28e3 ("perf/x86/intel/ds: Flush PEBS DS when changing PEBS_DATA_CFG")
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Cc: stable@vger.kernel.org
---
 arch/x86/events/intel/ds.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 8afc4ad3cd16..1a4b326ca2ce 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1489,7 +1489,7 @@ void intel_pmu_pebs_enable(struct perf_event *event)
 			 * hence we need to drain when changing said
 			 * size.
 			 */
-			intel_pmu_drain_large_pebs(cpuc);
+			intel_pmu_drain_pebs_buffer();
 			adaptive_pebs_record_size_update();
 			wrmsrl(MSR_PEBS_DATA_CFG, pebs_data_cfg);
 			cpuc->active_pebs_data_cfg = pebs_data_cfg;
-- 
2.38.1

[PATCH V2 2/4] perf/x86/intel/ds: Clarify adaptive PEBS processing

[kan.liang]

From: Kan Liang <kan.liang@linux.intel.com>

Modify the pebs_basic and pebs_meminfo structs to make the bitfields
more explicit to ease readability of the code.

Co-developed-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
---
 arch/x86/events/intel/ds.c        | 43 ++++++++++++++-----------------
 arch/x86/include/asm/perf_event.h | 16 ++++++++++--
 2 files changed, 34 insertions(+), 25 deletions(-)

diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 1a4b326ca2ce..35926d0d2341 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1917,8 +1917,6 @@ static void adaptive_pebs_save_regs(struct pt_regs *regs,
 }
 
 #define PEBS_LATENCY_MASK			0xffff
-#define PEBS_CACHE_LATENCY_OFFSET		32
-#define PEBS_RETIRE_LATENCY_OFFSET		32
 
 /*
  * With adaptive PEBS the layout depends on what fields are configured.
@@ -1932,8 +1930,7 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
 	struct pebs_basic *basic = __pebs;
 	void *next_record = basic + 1;
-	u64 sample_type;
-	u64 format_size;
+	u64 sample_type, format_group;
 	struct pebs_meminfo *meminfo = NULL;
 	struct pebs_gprs *gprs = NULL;
 	struct x86_perf_regs *perf_regs;
@@ -1945,7 +1942,7 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 	perf_regs->xmm_regs = NULL;
 
 	sample_type = event->attr.sample_type;
-	format_size = basic->format_size;
+	format_group = basic->format_group;
 	perf_sample_data_init(data, 0, event->hw.last_period);
 	data->period = event->hw.last_period;
 
@@ -1967,7 +1964,7 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 
 	if (sample_type & PERF_SAMPLE_WEIGHT_STRUCT) {
 		if (x86_pmu.flags & PMU_FL_RETIRE_LATENCY)
-			data->weight.var3_w = format_size >> PEBS_RETIRE_LATENCY_OFFSET & PEBS_LATENCY_MASK;
+			data->weight.var3_w = basic->retire_latency;
 		else
 			data->weight.var3_w = 0;
 	}
@@ -1977,12 +1974,12 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 	 * But PERF_SAMPLE_TRANSACTION needs gprs->ax.
 	 * Save the pointer here but process later.
 	 */
-	if (format_size & PEBS_DATACFG_MEMINFO) {
+	if (format_group & PEBS_DATACFG_MEMINFO) {
 		meminfo = next_record;
 		next_record = meminfo + 1;
 	}
 
-	if (format_size & PEBS_DATACFG_GP) {
+	if (format_group & PEBS_DATACFG_GP) {
 		gprs = next_record;
 		next_record = gprs + 1;
 
@@ -1995,14 +1992,13 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 			adaptive_pebs_save_regs(regs, gprs);
 	}
 
-	if (format_size & PEBS_DATACFG_MEMINFO) {
+	if (format_group & PEBS_DATACFG_MEMINFO) {
 		if (sample_type & PERF_SAMPLE_WEIGHT_TYPE) {
-			u64 weight = meminfo->latency;
+			u64 latency = x86_pmu.flags & PMU_FL_INSTR_LATENCY ?
+					meminfo->cache_latency : meminfo->mem_latency;
 
-			if (x86_pmu.flags & PMU_FL_INSTR_LATENCY) {
-				data->weight.var2_w = weight & PEBS_LATENCY_MASK;
-				weight >>= PEBS_CACHE_LATENCY_OFFSET;
-			}
+			if (x86_pmu.flags & PMU_FL_INSTR_LATENCY)
+				data->weight.var2_w = meminfo->instr_latency;
 
 			/*
 			 * Although meminfo::latency is defined as a u64,
@@ -2010,12 +2006,13 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 			 * in practice on Ice Lake and earlier platforms.
 			 */
 			if (sample_type & PERF_SAMPLE_WEIGHT) {
-				data->weight.full = weight ?:
+				data->weight.full = latency ?:
 					intel_get_tsx_weight(meminfo->tsx_tuning);
 			} else {
-				data->weight.var1_dw = (u32)(weight & PEBS_LATENCY_MASK) ?:
+				data->weight.var1_dw = (u32)latency ?:
 					intel_get_tsx_weight(meminfo->tsx_tuning);
 			}
+
 			data->sample_flags |= PERF_SAMPLE_WEIGHT_TYPE;
 		}
 
@@ -2036,16 +2033,16 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 		}
 	}
 
-	if (format_size & PEBS_DATACFG_XMMS) {
+	if (format_group & PEBS_DATACFG_XMMS) {
 		struct pebs_xmm *xmm = next_record;
 
 		next_record = xmm + 1;
 		perf_regs->xmm_regs = xmm->xmm;
 	}
 
-	if (format_size & PEBS_DATACFG_LBRS) {
+	if (format_group & PEBS_DATACFG_LBRS) {
 		struct lbr_entry *lbr = next_record;
-		int num_lbr = ((format_size >> PEBS_DATACFG_LBR_SHIFT)
+		int num_lbr = ((format_group >> PEBS_DATACFG_LBR_SHIFT)
 					& 0xff) + 1;
 		next_record = next_record + num_lbr * sizeof(struct lbr_entry);
 
@@ -2055,11 +2052,11 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 		}
 	}
 
-	WARN_ONCE(next_record != __pebs + (format_size >> 48),
-			"PEBS record size %llu, expected %llu, config %llx\n",
-			format_size >> 48,
+	WARN_ONCE(next_record != __pebs + basic->format_size,
+			"PEBS record size %u, expected %llu, config %llx\n",
+			basic->format_size,
 			(u64)(next_record - __pebs),
-			basic->format_size);
+			format_group);
 }
 
 static inline void *
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 91b73571412f..cd8023d5ea46 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -422,7 +422,9 @@ static inline bool is_topdown_idx(int idx)
  */
 
 struct pebs_basic {
-	u64 format_size;
+	u64 format_group:32,
+	    retire_latency:16,
+	    format_size:16;
 	u64 ip;
 	u64 applicable_counters;
 	u64 tsc;
@@ -431,7 +433,17 @@ struct pebs_basic {
 struct pebs_meminfo {
 	u64 address;
 	u64 aux;
-	u64 latency;
+	union {
+		/* pre Alder Lake */
+		u64 mem_latency;
+		/* Alder Lake and later */
+		struct {
+			u64 instr_latency:16;
+			u64 pad2:16;
+			u64 cache_latency:16;
+			u64 pad3:16;
+		};
+	};
 	u64 tsx_tuning;
 };
 
-- 
2.38.1

[PATCH V2 3/4] perf/x86/intel/ds: Factor out functions for PEBS records processing

[kan.liang]

From: Kan Liang <kan.liang@linux.intel.com>

Factor out functions to process normal and the last PEBS records, which
can be shared with the later patch.

Move the event updating related codes (intel_pmu_save_and_restart())
to the end, where all samples have been processed.
For the current usage, it doesn't matter when perf updates event counts
and reset the counter. Because all counters are stopped when the PEBS
buffer is drained.
Drop the return of the !intel_pmu_save_and_restart(event) check. Because
it never happen. The intel_pmu_save_and_restart(event) only returns 0,
when !hwc->event_base or the period_left > 0.
- The !hwc->event_base is impossible for the PEBS event, since the PEBS
  event is only available on GP and fixed counters, which always have
  a valid hwc->event_base.
- The check only happens for the case of non-AUTO_RELOAD and single
  PEBS, which implies that the event must be overflowed. The period_left
  must be always <= 0 for an overflowed event after the
  x86_pmu_update().

Co-developed-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
---
 arch/x86/events/intel/ds.c | 109 +++++++++++++++++++++++--------------
 1 file changed, 67 insertions(+), 42 deletions(-)

diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 35926d0d2341..bf624499f3b4 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -2167,46 +2167,33 @@ intel_pmu_save_and_restart_reload(struct perf_event *event, int count)
 	return 0;
 }
 
+typedef void (*setup_fn)(struct perf_event *, struct pt_regs *, void *,
+			 struct perf_sample_data *, struct pt_regs *);
+
+static struct pt_regs dummy_iregs;
+
 static __always_inline void
 __intel_pmu_pebs_event(struct perf_event *event,
 		       struct pt_regs *iregs,
+		       struct pt_regs *regs,
 		       struct perf_sample_data *data,
-		       void *base, void *top,
-		       int bit, int count,
-		       void (*setup_sample)(struct perf_event *,
-					    struct pt_regs *,
-					    void *,
-					    struct perf_sample_data *,
-					    struct pt_regs *))
+		       void *at,
+		       setup_fn setup_sample)
 {
-	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
-	struct hw_perf_event *hwc = &event->hw;
-	struct x86_perf_regs perf_regs;
-	struct pt_regs *regs = &perf_regs.regs;
-	void *at = get_next_pebs_record_by_bit(base, top, bit);
-	static struct pt_regs dummy_iregs;
-
-	if (hwc->flags & PERF_X86_EVENT_AUTO_RELOAD) {
-		/*
-		 * Now, auto-reload is only enabled in fixed period mode.
-		 * The reload value is always hwc->sample_period.
-		 * May need to change it, if auto-reload is enabled in
-		 * freq mode later.
-		 */
-		intel_pmu_save_and_restart_reload(event, count);
-	} else if (!intel_pmu_save_and_restart(event))
-		return;
-
-	if (!iregs)
-		iregs = &dummy_iregs;
+	setup_sample(event, iregs, at, data, regs);
+	perf_event_output(event, data, regs);
+}
 
-	while (count > 1) {
-		setup_sample(event, iregs, at, data, regs);
-		perf_event_output(event, data, regs);
-		at += cpuc->pebs_record_size;
-		at = get_next_pebs_record_by_bit(at, top, bit);
-		count--;
-	}
+static __always_inline void
+__intel_pmu_pebs_last_event(struct perf_event *event,
+			    struct pt_regs *iregs,
+			    struct pt_regs *regs,
+			    struct perf_sample_data *data,
+			    void *at,
+			    int count,
+			    setup_fn setup_sample)
+{
+	struct hw_perf_event *hwc = &event->hw;
 
 	setup_sample(event, iregs, at, data, regs);
 	if (iregs == &dummy_iregs) {
@@ -2225,6 +2212,44 @@ __intel_pmu_pebs_event(struct perf_event *event,
 		if (perf_event_overflow(event, data, regs))
 			x86_pmu_stop(event, 0);
 	}
+
+	if (hwc->flags & PERF_X86_EVENT_AUTO_RELOAD) {
+		/*
+		 * Now, auto-reload is only enabled in fixed period mode.
+		 * The reload value is always hwc->sample_period.
+		 * May need to change it, if auto-reload is enabled in
+		 * freq mode later.
+		 */
+		intel_pmu_save_and_restart_reload(event, count);
+	} else
+		intel_pmu_save_and_restart(event);
+}
+
+static __always_inline void
+__intel_pmu_pebs_events(struct perf_event *event,
+			struct pt_regs *iregs,
+			struct perf_sample_data *data,
+			void *base, void *top,
+			int bit, int count,
+			setup_fn setup_sample)
+{
+	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+	struct x86_perf_regs perf_regs;
+	struct pt_regs *regs = &perf_regs.regs;
+	void *at = get_next_pebs_record_by_bit(base, top, bit);
+	int cnt = count;
+
+	if (!iregs)
+		iregs = &dummy_iregs;
+
+	while (cnt > 1) {
+		__intel_pmu_pebs_event(event, iregs, regs, data, at, setup_sample);
+		at += cpuc->pebs_record_size;
+		at = get_next_pebs_record_by_bit(at, top, bit);
+		cnt--;
+	}
+
+	__intel_pmu_pebs_last_event(event, iregs, regs, data, at, count, setup_sample);
 }
 
 static void intel_pmu_drain_pebs_core(struct pt_regs *iregs, struct perf_sample_data *data)
@@ -2261,8 +2286,8 @@ static void intel_pmu_drain_pebs_core(struct pt_regs *iregs, struct perf_sample_
 		return;
 	}
 
-	__intel_pmu_pebs_event(event, iregs, data, at, top, 0, n,
-			       setup_pebs_fixed_sample_data);
+	__intel_pmu_pebs_events(event, iregs, data, at, top, 0, n,
+				setup_pebs_fixed_sample_data);
 }
 
 static void intel_pmu_pebs_event_update_no_drain(struct cpu_hw_events *cpuc, int size)
@@ -2393,9 +2418,9 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs, struct perf_sample_d
 		}
 
 		if (counts[bit]) {
-			__intel_pmu_pebs_event(event, iregs, data, base,
-					       top, bit, counts[bit],
-					       setup_pebs_fixed_sample_data);
+			__intel_pmu_pebs_events(event, iregs, data, base,
+						top, bit, counts[bit],
+						setup_pebs_fixed_sample_data);
 		}
 	}
 }
@@ -2447,9 +2472,9 @@ static void intel_pmu_drain_pebs_icl(struct pt_regs *iregs, struct perf_sample_d
 		if (WARN_ON_ONCE(!event->attr.precise_ip))
 			continue;
 
-		__intel_pmu_pebs_event(event, iregs, data, base,
-				       top, bit, counts[bit],
-				       setup_pebs_adaptive_sample_data);
+		__intel_pmu_pebs_events(event, iregs, data, base,
+					top, bit, counts[bit],
+					setup_pebs_adaptive_sample_data);
 	}
 }
 
-- 
2.38.1

[PATCH V2 4/4] perf/x86/intel/ds: Simplify the PEBS records processing for adaptive PEBS

[kan.liang]

From: Kan Liang <kan.liang@linux.intel.com>

The current code may iterate all the PEBS records in the DS area several
times. The first loop is to find all active events and calculate the
available records for each event. Then iterate the whole buffer again
and again to process available records until all active events are
processed.

The algorithm is inherited from the old generations. The old PEBS
hardware does not deal well with the situation when events happen near
each other. SW has to drop the error records. Multiple iterations are
required.

The hardware limit has been addressed on newer platforms with adaptive
PEBS. A simple one-iteration algorithm is introduced.

The samples are output by record order with the patch, rather than the
event order. It doesn't impact the post-processing. The perf tool always
sorts the records by time before presenting them to the end user.

In an NMI, the last record has to be specially handled. Add a last[]
variable to track the last unprocessed record of each event.

Test:

11 PEBS events are used in the perf test. Only the basic information is
collected.
perf record -e instructions:up,...,instructions:up -c 2000003 benchmark

The ftrace is used to record the duration of the
intel_pmu_drain_pebs_icl().

The average duration reduced from 62.04us to 57.94us.

A small improvement can be observed with the new algorithm.
Also, the implementation becomes simpler and more straightforward.

Suggested-by: Stephane Eranian <eranian@google.com>
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
---
 arch/x86/events/intel/ds.c | 43 +++++++++++++++++++++++++-------------
 1 file changed, 29 insertions(+), 14 deletions(-)

diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index bf624499f3b4..dc9fe45df297 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -2428,8 +2428,12 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs, struct perf_sample_d
 static void intel_pmu_drain_pebs_icl(struct pt_regs *iregs, struct perf_sample_data *data)
 {
 	short counts[INTEL_PMC_IDX_FIXED + MAX_FIXED_PEBS_EVENTS] = {};
+	void *last[INTEL_PMC_IDX_FIXED + MAX_FIXED_PEBS_EVENTS];
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
 	struct debug_store *ds = cpuc->ds;
+	struct x86_perf_regs perf_regs;
+	struct pt_regs *regs = &perf_regs.regs;
+	struct pebs_basic *basic;
 	struct perf_event *event;
 	void *base, *at, *top;
 	int bit;
@@ -2451,30 +2455,41 @@ static void intel_pmu_drain_pebs_icl(struct pt_regs *iregs, struct perf_sample_d
 		return;
 	}
 
-	for (at = base; at < top; at += cpuc->pebs_record_size) {
+	if (!iregs)
+		iregs = &dummy_iregs;
+
+	/* Process all but the last event for each counter. */
+	for (at = base; at < top; at += basic->format_size) {
 		u64 pebs_status;
 
-		pebs_status = get_pebs_status(at) & cpuc->pebs_enabled;
-		pebs_status &= mask;
+		basic = at;
+		if (basic->format_size != cpuc->pebs_record_size)
+			continue;
+
+		pebs_status = basic->applicable_counters & cpuc->pebs_enabled & mask;
+		for_each_set_bit(bit, (unsigned long *)&pebs_status, X86_PMC_IDX_MAX) {
+			event = cpuc->events[bit];
 
-		for_each_set_bit(bit, (unsigned long *)&pebs_status, X86_PMC_IDX_MAX)
-			counts[bit]++;
+			if (WARN_ON_ONCE(!event) ||
+			    WARN_ON_ONCE(!event->attr.precise_ip))
+				continue;
+
+			if (counts[bit]++) {
+				__intel_pmu_pebs_event(event, iregs, regs, data, last[bit],
+						       setup_pebs_adaptive_sample_data);
+			}
+			last[bit] = at;
+		}
 	}
 
 	for_each_set_bit(bit, (unsigned long *)&mask, X86_PMC_IDX_MAX) {
-		if (counts[bit] == 0)
+		if (!counts[bit])
 			continue;
 
 		event = cpuc->events[bit];
-		if (WARN_ON_ONCE(!event))
-			continue;
-
-		if (WARN_ON_ONCE(!event->attr.precise_ip))
-			continue;
 
-		__intel_pmu_pebs_events(event, iregs, data, base,
-					top, bit, counts[bit],
-					setup_pebs_adaptive_sample_data);
+		__intel_pmu_pebs_last_event(event, iregs, regs, data, last[bit],
+					    counts[bit], setup_pebs_adaptive_sample_data);
 	}
 }
 
-- 
2.38.1

[tip: perf/core] perf/x86/intel/ds: Simplify the PEBS records processing for adaptive PEBS

[tip-bot2 for Kan Liang]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     ae55e308bde2267df79c4475daa85e174b7ab4c8
Gitweb:        https://git.kernel.org/tip/ae55e308bde2267df79c4475daa85e174b7ab4c8
Author:        Kan Liang <kan.liang@linux.intel.com>
AuthorDate:    Tue, 19 Nov 2024 05:55:04 -08:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 02 Dec 2024 12:01:34 +01:00

perf/x86/intel/ds: Simplify the PEBS records processing for adaptive PEBS

The current code may iterate all the PEBS records in the DS area several
times. The first loop is to find all active events and calculate the
available records for each event. Then iterate the whole buffer again
and again to process available records until all active events are
processed.

The algorithm is inherited from the old generations. The old PEBS
hardware does not deal well with the situation when events happen near
each other. SW has to drop the error records. Multiple iterations are
required.

The hardware limit has been addressed on newer platforms with adaptive
PEBS. A simple one-iteration algorithm is introduced.

The samples are output by record order with the patch, rather than the
event order. It doesn't impact the post-processing. The perf tool always
sorts the records by time before presenting them to the end user.

In an NMI, the last record has to be specially handled. Add a last[]
variable to track the last unprocessed record of each event.

Test:

11 PEBS events are used in the perf test. Only the basic information is
collected.
perf record -e instructions:up,...,instructions:up -c 2000003 benchmark

The ftrace is used to record the duration of the
intel_pmu_drain_pebs_icl().

The average duration reduced from 62.04us to 57.94us.

A small improvement can be observed with the new algorithm.
Also, the implementation becomes simpler and more straightforward.

Suggested-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20241119135504.1463839-5-kan.liang@linux.intel.com
---
 arch/x86/events/intel/ds.c | 43 ++++++++++++++++++++++++-------------
 1 file changed, 29 insertions(+), 14 deletions(-)

diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 79a3467..8dcf90f 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -2425,8 +2425,12 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs, struct perf_sample_d
 static void intel_pmu_drain_pebs_icl(struct pt_regs *iregs, struct perf_sample_data *data)
 {
 	short counts[INTEL_PMC_IDX_FIXED + MAX_FIXED_PEBS_EVENTS] = {};
+	void *last[INTEL_PMC_IDX_FIXED + MAX_FIXED_PEBS_EVENTS];
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
 	struct debug_store *ds = cpuc->ds;
+	struct x86_perf_regs perf_regs;
+	struct pt_regs *regs = &perf_regs.regs;
+	struct pebs_basic *basic;
 	struct perf_event *event;
 	void *base, *at, *top;
 	int bit;
@@ -2448,30 +2452,41 @@ static void intel_pmu_drain_pebs_icl(struct pt_regs *iregs, struct perf_sample_d
 		return;
 	}
 
-	for (at = base; at < top; at += cpuc->pebs_record_size) {
+	if (!iregs)
+		iregs = &dummy_iregs;
+
+	/* Process all but the last event for each counter. */
+	for (at = base; at < top; at += basic->format_size) {
 		u64 pebs_status;
 
-		pebs_status = get_pebs_status(at) & cpuc->pebs_enabled;
-		pebs_status &= mask;
+		basic = at;
+		if (basic->format_size != cpuc->pebs_record_size)
+			continue;
+
+		pebs_status = basic->applicable_counters & cpuc->pebs_enabled & mask;
+		for_each_set_bit(bit, (unsigned long *)&pebs_status, X86_PMC_IDX_MAX) {
+			event = cpuc->events[bit];
 
-		for_each_set_bit(bit, (unsigned long *)&pebs_status, X86_PMC_IDX_MAX)
-			counts[bit]++;
+			if (WARN_ON_ONCE(!event) ||
+			    WARN_ON_ONCE(!event->attr.precise_ip))
+				continue;
+
+			if (counts[bit]++) {
+				__intel_pmu_pebs_event(event, iregs, regs, data, last[bit],
+						       setup_pebs_adaptive_sample_data);
+			}
+			last[bit] = at;
+		}
 	}
 
 	for_each_set_bit(bit, (unsigned long *)&mask, X86_PMC_IDX_MAX) {
-		if (counts[bit] == 0)
+		if (!counts[bit])
 			continue;
 
 		event = cpuc->events[bit];
-		if (WARN_ON_ONCE(!event))
-			continue;
-
-		if (WARN_ON_ONCE(!event->attr.precise_ip))
-			continue;
 
-		__intel_pmu_pebs_events(event, iregs, data, base,
-					top, bit, counts[bit],
-					setup_pebs_adaptive_sample_data);
+		__intel_pmu_pebs_last_event(event, iregs, regs, data, last[bit],
+					    counts[bit], setup_pebs_adaptive_sample_data);
 	}
 }
 

[tip: perf/core] perf/x86/intel/ds: Factor out functions for PEBS records processing

[tip-bot2 for Kan Liang]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     3c00ed344cef4dbb57d8769b961af414132a173a
Gitweb:        https://git.kernel.org/tip/3c00ed344cef4dbb57d8769b961af414132a173a
Author:        Kan Liang <kan.liang@linux.intel.com>
AuthorDate:    Tue, 19 Nov 2024 05:55:03 -08:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 02 Dec 2024 12:01:34 +01:00

perf/x86/intel/ds: Factor out functions for PEBS records processing

Factor out functions to process normal and the last PEBS records, which
can be shared with the later patch.

Move the event updating related codes (intel_pmu_save_and_restart())
to the end, where all samples have been processed.
For the current usage, it doesn't matter when perf updates event counts
and reset the counter. Because all counters are stopped when the PEBS
buffer is drained.
Drop the return of the !intel_pmu_save_and_restart(event) check. Because
it never happen. The intel_pmu_save_and_restart(event) only returns 0,
when !hwc->event_base or the period_left > 0.
- The !hwc->event_base is impossible for the PEBS event, since the PEBS
  event is only available on GP and fixed counters, which always have
  a valid hwc->event_base.
- The check only happens for the case of non-AUTO_RELOAD and single
  PEBS, which implies that the event must be overflowed. The period_left
  must be always <= 0 for an overflowed event after the
  x86_pmu_update().

Co-developed-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241119135504.1463839-4-kan.liang@linux.intel.com
---
 arch/x86/events/intel/ds.c | 109 ++++++++++++++++++++++--------------
 1 file changed, 67 insertions(+), 42 deletions(-)

diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 450f318..79a3467 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -2164,46 +2164,33 @@ intel_pmu_save_and_restart_reload(struct perf_event *event, int count)
 	return 0;
 }
 
+typedef void (*setup_fn)(struct perf_event *, struct pt_regs *, void *,
+			 struct perf_sample_data *, struct pt_regs *);
+
+static struct pt_regs dummy_iregs;
+
 static __always_inline void
 __intel_pmu_pebs_event(struct perf_event *event,
 		       struct pt_regs *iregs,
+		       struct pt_regs *regs,
 		       struct perf_sample_data *data,
-		       void *base, void *top,
-		       int bit, int count,
-		       void (*setup_sample)(struct perf_event *,
-					    struct pt_regs *,
-					    void *,
-					    struct perf_sample_data *,
-					    struct pt_regs *))
+		       void *at,
+		       setup_fn setup_sample)
 {
-	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
-	struct hw_perf_event *hwc = &event->hw;
-	struct x86_perf_regs perf_regs;
-	struct pt_regs *regs = &perf_regs.regs;
-	void *at = get_next_pebs_record_by_bit(base, top, bit);
-	static struct pt_regs dummy_iregs;
-
-	if (hwc->flags & PERF_X86_EVENT_AUTO_RELOAD) {
-		/*
-		 * Now, auto-reload is only enabled in fixed period mode.
-		 * The reload value is always hwc->sample_period.
-		 * May need to change it, if auto-reload is enabled in
-		 * freq mode later.
-		 */
-		intel_pmu_save_and_restart_reload(event, count);
-	} else if (!intel_pmu_save_and_restart(event))
-		return;
-
-	if (!iregs)
-		iregs = &dummy_iregs;
+	setup_sample(event, iregs, at, data, regs);
+	perf_event_output(event, data, regs);
+}
 
-	while (count > 1) {
-		setup_sample(event, iregs, at, data, regs);
-		perf_event_output(event, data, regs);
-		at += cpuc->pebs_record_size;
-		at = get_next_pebs_record_by_bit(at, top, bit);
-		count--;
-	}
+static __always_inline void
+__intel_pmu_pebs_last_event(struct perf_event *event,
+			    struct pt_regs *iregs,
+			    struct pt_regs *regs,
+			    struct perf_sample_data *data,
+			    void *at,
+			    int count,
+			    setup_fn setup_sample)
+{
+	struct hw_perf_event *hwc = &event->hw;
 
 	setup_sample(event, iregs, at, data, regs);
 	if (iregs == &dummy_iregs) {
@@ -2222,6 +2209,44 @@ __intel_pmu_pebs_event(struct perf_event *event,
 		if (perf_event_overflow(event, data, regs))
 			x86_pmu_stop(event, 0);
 	}
+
+	if (hwc->flags & PERF_X86_EVENT_AUTO_RELOAD) {
+		/*
+		 * Now, auto-reload is only enabled in fixed period mode.
+		 * The reload value is always hwc->sample_period.
+		 * May need to change it, if auto-reload is enabled in
+		 * freq mode later.
+		 */
+		intel_pmu_save_and_restart_reload(event, count);
+	} else
+		intel_pmu_save_and_restart(event);
+}
+
+static __always_inline void
+__intel_pmu_pebs_events(struct perf_event *event,
+			struct pt_regs *iregs,
+			struct perf_sample_data *data,
+			void *base, void *top,
+			int bit, int count,
+			setup_fn setup_sample)
+{
+	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+	struct x86_perf_regs perf_regs;
+	struct pt_regs *regs = &perf_regs.regs;
+	void *at = get_next_pebs_record_by_bit(base, top, bit);
+	int cnt = count;
+
+	if (!iregs)
+		iregs = &dummy_iregs;
+
+	while (cnt > 1) {
+		__intel_pmu_pebs_event(event, iregs, regs, data, at, setup_sample);
+		at += cpuc->pebs_record_size;
+		at = get_next_pebs_record_by_bit(at, top, bit);
+		cnt--;
+	}
+
+	__intel_pmu_pebs_last_event(event, iregs, regs, data, at, count, setup_sample);
 }
 
 static void intel_pmu_drain_pebs_core(struct pt_regs *iregs, struct perf_sample_data *data)
@@ -2258,8 +2283,8 @@ static void intel_pmu_drain_pebs_core(struct pt_regs *iregs, struct perf_sample_
 		return;
 	}
 
-	__intel_pmu_pebs_event(event, iregs, data, at, top, 0, n,
-			       setup_pebs_fixed_sample_data);
+	__intel_pmu_pebs_events(event, iregs, data, at, top, 0, n,
+				setup_pebs_fixed_sample_data);
 }
 
 static void intel_pmu_pebs_event_update_no_drain(struct cpu_hw_events *cpuc, int size)
@@ -2390,9 +2415,9 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs, struct perf_sample_d
 		}
 
 		if (counts[bit]) {
-			__intel_pmu_pebs_event(event, iregs, data, base,
-					       top, bit, counts[bit],
-					       setup_pebs_fixed_sample_data);
+			__intel_pmu_pebs_events(event, iregs, data, base,
+						top, bit, counts[bit],
+						setup_pebs_fixed_sample_data);
 		}
 	}
 }
@@ -2444,9 +2469,9 @@ static void intel_pmu_drain_pebs_icl(struct pt_regs *iregs, struct perf_sample_d
 		if (WARN_ON_ONCE(!event->attr.precise_ip))
 			continue;
 
-		__intel_pmu_pebs_event(event, iregs, data, base,
-				       top, bit, counts[bit],
-				       setup_pebs_adaptive_sample_data);
+		__intel_pmu_pebs_events(event, iregs, data, base,
+					top, bit, counts[bit],
+					setup_pebs_adaptive_sample_data);
 	}
 }
 

[tip: perf/core] perf/x86/intel/ds: Clarify adaptive PEBS processing

[tip-bot2 for Kan Liang]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     7087bfb0adc9a12ec3b463b1d38072c5efce5d6c
Gitweb:        https://git.kernel.org/tip/7087bfb0adc9a12ec3b463b1d38072c5efce5d6c
Author:        Kan Liang <kan.liang@linux.intel.com>
AuthorDate:    Tue, 19 Nov 2024 05:55:02 -08:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 02 Dec 2024 12:01:34 +01:00

perf/x86/intel/ds: Clarify adaptive PEBS processing

Modify the pebs_basic and pebs_meminfo structs to make the bitfields
more explicit to ease readability of the code.

Co-developed-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241119135504.1463839-3-kan.liang@linux.intel.com
---
 arch/x86/events/intel/ds.c        | 43 +++++++++++++-----------------
 arch/x86/include/asm/perf_event.h | 16 +++++++++--
 2 files changed, 34 insertions(+), 25 deletions(-)

diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 34cba39..450f318 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1915,8 +1915,6 @@ static void adaptive_pebs_save_regs(struct pt_regs *regs,
 }
 
 #define PEBS_LATENCY_MASK			0xffff
-#define PEBS_CACHE_LATENCY_OFFSET		32
-#define PEBS_RETIRE_LATENCY_OFFSET		32
 
 /*
  * With adaptive PEBS the layout depends on what fields are configured.
@@ -1930,8 +1928,7 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
 	struct pebs_basic *basic = __pebs;
 	void *next_record = basic + 1;
-	u64 sample_type;
-	u64 format_size;
+	u64 sample_type, format_group;
 	struct pebs_meminfo *meminfo = NULL;
 	struct pebs_gprs *gprs = NULL;
 	struct x86_perf_regs *perf_regs;
@@ -1943,7 +1940,7 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 	perf_regs->xmm_regs = NULL;
 
 	sample_type = event->attr.sample_type;
-	format_size = basic->format_size;
+	format_group = basic->format_group;
 	perf_sample_data_init(data, 0, event->hw.last_period);
 	data->period = event->hw.last_period;
 
@@ -1964,7 +1961,7 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 
 	if (sample_type & PERF_SAMPLE_WEIGHT_STRUCT) {
 		if (x86_pmu.flags & PMU_FL_RETIRE_LATENCY)
-			data->weight.var3_w = format_size >> PEBS_RETIRE_LATENCY_OFFSET & PEBS_LATENCY_MASK;
+			data->weight.var3_w = basic->retire_latency;
 		else
 			data->weight.var3_w = 0;
 	}
@@ -1974,12 +1971,12 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 	 * But PERF_SAMPLE_TRANSACTION needs gprs->ax.
 	 * Save the pointer here but process later.
 	 */
-	if (format_size & PEBS_DATACFG_MEMINFO) {
+	if (format_group & PEBS_DATACFG_MEMINFO) {
 		meminfo = next_record;
 		next_record = meminfo + 1;
 	}
 
-	if (format_size & PEBS_DATACFG_GP) {
+	if (format_group & PEBS_DATACFG_GP) {
 		gprs = next_record;
 		next_record = gprs + 1;
 
@@ -1992,14 +1989,13 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 			adaptive_pebs_save_regs(regs, gprs);
 	}
 
-	if (format_size & PEBS_DATACFG_MEMINFO) {
+	if (format_group & PEBS_DATACFG_MEMINFO) {
 		if (sample_type & PERF_SAMPLE_WEIGHT_TYPE) {
-			u64 weight = meminfo->latency;
+			u64 latency = x86_pmu.flags & PMU_FL_INSTR_LATENCY ?
+					meminfo->cache_latency : meminfo->mem_latency;
 
-			if (x86_pmu.flags & PMU_FL_INSTR_LATENCY) {
-				data->weight.var2_w = weight & PEBS_LATENCY_MASK;
-				weight >>= PEBS_CACHE_LATENCY_OFFSET;
-			}
+			if (x86_pmu.flags & PMU_FL_INSTR_LATENCY)
+				data->weight.var2_w = meminfo->instr_latency;
 
 			/*
 			 * Although meminfo::latency is defined as a u64,
@@ -2007,12 +2003,13 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 			 * in practice on Ice Lake and earlier platforms.
 			 */
 			if (sample_type & PERF_SAMPLE_WEIGHT) {
-				data->weight.full = weight ?:
+				data->weight.full = latency ?:
 					intel_get_tsx_weight(meminfo->tsx_tuning);
 			} else {
-				data->weight.var1_dw = (u32)(weight & PEBS_LATENCY_MASK) ?:
+				data->weight.var1_dw = (u32)latency ?:
 					intel_get_tsx_weight(meminfo->tsx_tuning);
 			}
+
 			data->sample_flags |= PERF_SAMPLE_WEIGHT_TYPE;
 		}
 
@@ -2033,16 +2030,16 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 		}
 	}
 
-	if (format_size & PEBS_DATACFG_XMMS) {
+	if (format_group & PEBS_DATACFG_XMMS) {
 		struct pebs_xmm *xmm = next_record;
 
 		next_record = xmm + 1;
 		perf_regs->xmm_regs = xmm->xmm;
 	}
 
-	if (format_size & PEBS_DATACFG_LBRS) {
+	if (format_group & PEBS_DATACFG_LBRS) {
 		struct lbr_entry *lbr = next_record;
-		int num_lbr = ((format_size >> PEBS_DATACFG_LBR_SHIFT)
+		int num_lbr = ((format_group >> PEBS_DATACFG_LBR_SHIFT)
 					& 0xff) + 1;
 		next_record = next_record + num_lbr * sizeof(struct lbr_entry);
 
@@ -2052,11 +2049,11 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 		}
 	}
 
-	WARN_ONCE(next_record != __pebs + (format_size >> 48),
-			"PEBS record size %llu, expected %llu, config %llx\n",
-			format_size >> 48,
+	WARN_ONCE(next_record != __pebs + basic->format_size,
+			"PEBS record size %u, expected %llu, config %llx\n",
+			basic->format_size,
 			(u64)(next_record - __pebs),
-			basic->format_size);
+			format_group);
 }
 
 static inline void *
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index d95f902..cb9c467 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -422,7 +422,9 @@ static inline bool is_topdown_idx(int idx)
  */
 
 struct pebs_basic {
-	u64 format_size;
+	u64 format_group:32,
+	    retire_latency:16,
+	    format_size:16;
 	u64 ip;
 	u64 applicable_counters;
 	u64 tsc;
@@ -431,7 +433,17 @@ struct pebs_basic {
 struct pebs_meminfo {
 	u64 address;
 	u64 aux;
-	u64 latency;
+	union {
+		/* pre Alder Lake */
+		u64 mem_latency;
+		/* Alder Lake and later */
+		struct {
+			u64 instr_latency:16;
+			u64 pad2:16;
+			u64 cache_latency:16;
+			u64 pad3:16;
+		};
+	};
 	u64 tsx_tuning;
 };
 

[tip: perf/core] perf/x86/intel/ds: Unconditionally drain PEBS DS when changing PEBS_DATA_CFG

[tip-bot2 for Kan Liang]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     9f3de72a0c37005f897d69e4bdd59c25b8898447
Gitweb:        https://git.kernel.org/tip/9f3de72a0c37005f897d69e4bdd59c25b8898447
Author:        Kan Liang <kan.liang@linux.intel.com>
AuthorDate:    Tue, 19 Nov 2024 05:55:01 -08:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 02 Dec 2024 12:01:33 +01:00

perf/x86/intel/ds: Unconditionally drain PEBS DS when changing PEBS_DATA_CFG

The PEBS kernel warnings can still be observed with the below case.

when the below commands are running in parallel for a while.

  while true;
  do
	perf record --no-buildid -a --intr-regs=AX  \
		    -e cpu/event=0xd0,umask=0x81/pp \
		    -c 10003 -o /dev/null ./triad;
  done &

  while true;
  do
	perf record -e 'cpu/mem-loads,ldlat=3/uP' -W -d -- ./dtlb
  done

The commit b752ea0c28e3 ("perf/x86/intel/ds: Flush PEBS DS when changing
PEBS_DATA_CFG") intends to flush the entire PEBS buffer before the
hardware is reprogrammed. However, it fails in the above case.

The first perf command utilizes the large PEBS, while the second perf
command only utilizes a single PEBS. When the second perf event is
added, only the n_pebs++. The intel_pmu_pebs_enable() is invoked after
intel_pmu_pebs_add(). So the cpuc->n_pebs == cpuc->n_large_pebs check in
the intel_pmu_drain_large_pebs() fails. The PEBS DS is not flushed.
The new PEBS event should not be taken into account when flushing the
existing PEBS DS.

The check is unnecessary here. Before the hardware is reprogrammed, all
the stale records must be drained unconditionally.

For single PEBS or PEBS-vi-pt, the DS must be empty. The drain_pebs()
can handle the empty case. There is no harm to unconditionally drain the
PEBS DS.

Fixes: b752ea0c28e3 ("perf/x86/intel/ds: Flush PEBS DS when changing PEBS_DATA_CFG")
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20241119135504.1463839-2-kan.liang@linux.intel.com
---
 arch/x86/events/intel/ds.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 8afc4ad..1a4b326 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1489,7 +1489,7 @@ void intel_pmu_pebs_enable(struct perf_event *event)
 			 * hence we need to drain when changing said
 			 * size.
 			 */
-			intel_pmu_drain_large_pebs(cpuc);
+			intel_pmu_drain_pebs_buffer();
 			adaptive_pebs_record_size_update();
 			wrmsrl(MSR_PEBS_DATA_CFG, pebs_data_cfg);
 			cpuc->active_pebs_data_cfg = pebs_data_cfg;