perf sample: Make user_regs and intr_regs optional

The struct dump_regs contains 512 bytes of cache_regs, meaning the two
values in perf_sample contribute 1088 bytes of its total 1384 bytes
size. Initializing this much memory has a cost reported by Tavian
Barnes <tavianator@tavianator.com> as about 2.5% when running `perf
script --itrace=i0`:
https://lore.kernel.org/lkml/d841b97b3ad2ca8bcab07e4293375fb7c32dfce7.1736618095.git.tavianator@tavianator.com/

Adrian Hunter <adrian.hunter@intel.com> replied that the zero
initialization was necessary and couldn't simply be removed.

This patch aims to strike a middle ground of still zeroing the
perf_sample, but removing 79% of its size by make user_regs and
intr_regs optional pointers to zalloc-ed memory. To support the
allocation accessors are created for user_regs and intr_regs. To
support correct cleanup perf_sample__init and perf_sample__exit
functions are created and added throughout the code base.

Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250113194345.1537821-1-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

1 files changed, 94 insertions, 42 deletions

diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
index 30be6dfe09eb..4e8a9b172fbc 100644
--- a/tools/perf/util/intel-pt.c
+++ b/tools/perf/util/intel-pt.c
@@ -1764,12 +1764,13 @@ static int intel_pt_synth_branch_sample(struct intel_pt_queue *ptq)
 {
 	struct intel_pt *pt = ptq->pt;
 	union perf_event *event = ptq->event_buf;
-	struct perf_sample sample = { .ip = 0, };
+	struct perf_sample sample;
 	struct dummy_branch_stack {
 		u64			nr;
 		u64			hw_idx;
 		struct branch_entry	entries;
 	} dummy_bs;
+	int ret;
 
 	if (pt->branches_filter && !(pt->branches_filter & ptq->flags))
 		return 0;
@@ -1777,6 +1778,7 @@ static int intel_pt_synth_branch_sample(struct intel_pt_queue *ptq)
 	if (intel_pt_skip_event(pt))
 		return 0;
 
+	perf_sample__init(&sample, /*all=*/true);
 	intel_pt_prep_b_sample(pt, ptq, event, &sample);
 
 	sample.id = ptq->pt->branches_id;
@@ -1806,8 +1808,10 @@ static int intel_pt_synth_branch_sample(struct intel_pt_queue *ptq)
 		ptq->last_br_cyc_cnt = ptq->ipc_cyc_cnt;
 	}
 
-	return intel_pt_deliver_synth_event(pt, event, &sample,
+	perf_sample__exit(&sample);
+	ret = intel_pt_deliver_synth_event(pt, event, &sample,
 					    pt->branches_sample_type);
+	return ret;
 }
 
 static void intel_pt_prep_sample(struct intel_pt *pt,
@@ -1835,11 +1839,13 @@ static int intel_pt_synth_instruction_sample(struct intel_pt_queue *ptq)
 {
 	struct intel_pt *pt = ptq->pt;
 	union perf_event *event = ptq->event_buf;
-	struct perf_sample sample = { .ip = 0, };
+	struct perf_sample sample;
+	int ret;
 
 	if (intel_pt_skip_event(pt))
 		return 0;
 
+	perf_sample__init(&sample, /*all=*/true);
 	intel_pt_prep_sample(pt, ptq, event, &sample);
 
 	sample.id = ptq->pt->instructions_id;
@@ -1859,16 +1865,19 @@ static int intel_pt_synth_instruction_sample(struct intel_pt_queue *ptq)
 
 	ptq->last_insn_cnt = ptq->state->tot_insn_cnt;
 
-	return intel_pt_deliver_synth_event(pt, event, &sample,
-					    pt->instructions_sample_type);
+	ret = intel_pt_deliver_synth_event(pt, event, &sample,
+					   pt->instructions_sample_type);
+	perf_sample__exit(&sample);
+	return ret;
 }
 
 static int intel_pt_synth_cycle_sample(struct intel_pt_queue *ptq)
 {
 	struct intel_pt *pt = ptq->pt;
 	union perf_event *event = ptq->event_buf;
-	struct perf_sample sample = { .ip = 0, };
+	struct perf_sample sample;
 	u64 period = 0;
+	int ret;
 
 	if (ptq->sample_ipc)
 		period = ptq->ipc_cyc_cnt - ptq->last_cy_cyc_cnt;
@@ -1876,6 +1885,7 @@ static int intel_pt_synth_cycle_sample(struct intel_pt_queue *ptq)
 	if (!period || intel_pt_skip_event(pt))
 		return 0;
 
+	perf_sample__init(&sample, /*all=*/true);
 	intel_pt_prep_sample(pt, ptq, event, &sample);
 
 	sample.id = ptq->pt->cycles_id;
@@ -1887,25 +1897,31 @@ static int intel_pt_synth_cycle_sample(struct intel_pt_queue *ptq)
 	ptq->last_cy_insn_cnt = ptq->ipc_insn_cnt;
 	ptq->last_cy_cyc_cnt = ptq->ipc_cyc_cnt;
 
-	return intel_pt_deliver_synth_event(pt, event, &sample, pt->cycles_sample_type);
+	ret = intel_pt_deliver_synth_event(pt, event, &sample, pt->cycles_sample_type);
+	perf_sample__exit(&sample);
+	return ret;
 }
 
 static int intel_pt_synth_transaction_sample(struct intel_pt_queue *ptq)
 {
 	struct intel_pt *pt = ptq->pt;
 	union perf_event *event = ptq->event_buf;
-	struct perf_sample sample = { .ip = 0, };
+	struct perf_sample sample;
+	int ret;
 
 	if (intel_pt_skip_event(pt))
 		return 0;
 
+	perf_sample__init(&sample, /*all=*/true);
 	intel_pt_prep_sample(pt, ptq, event, &sample);
 
 	sample.id = ptq->pt->transactions_id;
 	sample.stream_id = ptq->pt->transactions_id;
 
-	return intel_pt_deliver_synth_event(pt, event, &sample,
-					    pt->transactions_sample_type);
+	ret = intel_pt_deliver_synth_event(pt, event, &sample,
+					   pt->transactions_sample_type);
+	perf_sample__exit(&sample);
+	return ret;
 }
 
 static void intel_pt_prep_p_sample(struct intel_pt *pt,
@@ -1953,15 +1969,17 @@ static int intel_pt_synth_cbr_sample(struct intel_pt_queue *ptq)
 {
 	struct intel_pt *pt = ptq->pt;
 	union perf_event *event = ptq->event_buf;
-	struct perf_sample sample = { .ip = 0, };
+	struct perf_sample sample;
 	struct perf_synth_intel_cbr raw;
 	u32 flags;
+	int ret;
 
 	if (intel_pt_skip_cbr_event(pt))
 		return 0;
 
 	ptq->cbr_seen = ptq->state->cbr;
 
+	perf_sample__init(&sample, /*all=*/true);
 	intel_pt_prep_p_sample(pt, ptq, event, &sample);
 
 	sample.id = ptq->pt->cbr_id;
@@ -1975,20 +1993,24 @@ static int intel_pt_synth_cbr_sample(struct intel_pt_queue *ptq)
 	sample.raw_size = perf_synth__raw_size(raw);
 	sample.raw_data = perf_synth__raw_data(&raw);
 
-	return intel_pt_deliver_synth_event(pt, event, &sample,
-					    pt->pwr_events_sample_type);
+	ret = intel_pt_deliver_synth_event(pt, event, &sample,
+					   pt->pwr_events_sample_type);
+	perf_sample__exit(&sample);
+	return ret;
 }
 
 static int intel_pt_synth_psb_sample(struct intel_pt_queue *ptq)
 {
 	struct intel_pt *pt = ptq->pt;
 	union perf_event *event = ptq->event_buf;
-	struct perf_sample sample = { .ip = 0, };
+	struct perf_sample sample;
 	struct perf_synth_intel_psb raw;
+	int ret;
 
 	if (intel_pt_skip_event(pt))
 		return 0;
 
+	perf_sample__init(&sample, /*all=*/true);
 	intel_pt_prep_p_sample(pt, ptq, event, &sample);
 
 	sample.id = ptq->pt->psb_id;
@@ -2001,20 +2023,24 @@ static int intel_pt_synth_psb_sample(struct intel_pt_queue *ptq)
 	sample.raw_size = perf_synth__raw_size(raw);
 	sample.raw_data = perf_synth__raw_data(&raw);
 
-	return intel_pt_deliver_synth_event(pt, event, &sample,
-					    pt->pwr_events_sample_type);
+	ret = intel_pt_deliver_synth_event(pt, event, &sample,
+					   pt->pwr_events_sample_type);
+	perf_sample__exit(&sample);
+	return ret;
 }
 
 static int intel_pt_synth_mwait_sample(struct intel_pt_queue *ptq)
 {
 	struct intel_pt *pt = ptq->pt;
 	union perf_event *event = ptq->event_buf;
-	struct perf_sample sample = { .ip = 0, };
+	struct perf_sample sample;
 	struct perf_synth_intel_mwait raw;
+	int ret;
 
 	if (intel_pt_skip_event(pt))
 		return 0;
 
+	perf_sample__init(&sample, /*all=*/true);
 	intel_pt_prep_p_sample(pt, ptq, event, &sample);
 
 	sample.id = ptq->pt->mwait_id;
@@ -2026,20 +2052,24 @@ static int intel_pt_synth_mwait_sample(struct intel_pt_queue *ptq)
 	sample.raw_size = perf_synth__raw_size(raw);
 	sample.raw_data = perf_synth__raw_data(&raw);
 
-	return intel_pt_deliver_synth_event(pt, event, &sample,
-					    pt->pwr_events_sample_type);
+	ret = intel_pt_deliver_synth_event(pt, event, &sample,
+					   pt->pwr_events_sample_type);
+	perf_sample__exit(&sample);
+	return ret;
 }
 
 static int intel_pt_synth_pwre_sample(struct intel_pt_queue *ptq)
 {
 	struct intel_pt *pt = ptq->pt;
 	union perf_event *event = ptq->event_buf;
-	struct perf_sample sample = { .ip = 0, };
+	struct perf_sample sample;
 	struct perf_synth_intel_pwre raw;
+	int ret;
 
 	if (intel_pt_skip_event(pt))
 		return 0;
 
+	perf_sample__init(&sample, /*all=*/true);
 	intel_pt_prep_p_sample(pt, ptq, event, &sample);
 
 	sample.id = ptq->pt->pwre_id;
@@ -2051,20 +2081,24 @@ static int intel_pt_synth_pwre_sample(struct intel_pt_queue *ptq)
 	sample.raw_size = perf_synth__raw_size(raw);
 	sample.raw_data = perf_synth__raw_data(&raw);
 
-	return intel_pt_deliver_synth_event(pt, event, &sample,
-					    pt->pwr_events_sample_type);
+	ret = intel_pt_deliver_synth_event(pt, event, &sample,
+					   pt->pwr_events_sample_type);
+	perf_sample__exit(&sample);
+	return ret;
 }
 
 static int intel_pt_synth_exstop_sample(struct intel_pt_queue *ptq)
 {
 	struct intel_pt *pt = ptq->pt;
 	union perf_event *event = ptq->event_buf;
-	struct perf_sample sample = { .ip = 0, };
+	struct perf_sample sample;
 	struct perf_synth_intel_exstop raw;
+	int ret;
 
 	if (intel_pt_skip_event(pt))
 		return 0;
 
+	perf_sample__init(&sample, /*all=*/true);
 	intel_pt_prep_p_sample(pt, ptq, event, &sample);
 
 	sample.id = ptq->pt->exstop_id;
@@ -2076,20 +2110,24 @@ static int intel_pt_synth_exstop_sample(struct intel_pt_queue *ptq)
 	sample.raw_size = perf_synth__raw_size(raw);
 	sample.raw_data = perf_synth__raw_data(&raw);
 
-	return intel_pt_deliver_synth_event(pt, event, &sample,
-					    pt->pwr_events_sample_type);
+	ret = intel_pt_deliver_synth_event(pt, event, &sample,
+					   pt->pwr_events_sample_type);
+	perf_sample__exit(&sample);
+	return ret;
 }
 
 static int intel_pt_synth_pwrx_sample(struct intel_pt_queue *ptq)
 {
 	struct intel_pt *pt = ptq->pt;
 	union perf_event *event = ptq->event_buf;
-	struct perf_sample sample = { .ip = 0, };
+	struct perf_sample sample;
 	struct perf_synth_intel_pwrx raw;
+	int ret;
 
 	if (intel_pt_skip_event(pt))
 		return 0;
 
+	perf_sample__init(&sample, /*all=*/true);
 	intel_pt_prep_p_sample(pt, ptq, event, &sample);
 
 	sample.id = ptq->pt->pwrx_id;
@@ -2101,8 +2139,10 @@ static int intel_pt_synth_pwrx_sample(struct intel_pt_queue *ptq)
 	sample.raw_size = perf_synth__raw_size(raw);
 	sample.raw_data = perf_synth__raw_data(&raw);
 
-	return intel_pt_deliver_synth_event(pt, event, &sample,
-					    pt->pwr_events_sample_type);
+	ret = intel_pt_deliver_synth_event(pt, event, &sample,
+					   pt->pwr_events_sample_type);
+	perf_sample__exit(&sample);
+	return ret;
 }
 
 /*
@@ -2235,16 +2275,18 @@ static void intel_pt_add_lbrs(struct branch_stack *br_stack,
 static int intel_pt_do_synth_pebs_sample(struct intel_pt_queue *ptq, struct evsel *evsel, u64 id)
 {
 	const struct intel_pt_blk_items *items = &ptq->state->items;
-	struct perf_sample sample = { .ip = 0, };
+	struct perf_sample sample;
 	union perf_event *event = ptq->event_buf;
 	struct intel_pt *pt = ptq->pt;
 	u64 sample_type = evsel->core.attr.sample_type;
 	u8 cpumode;
-	u64 regs[8 * sizeof(sample.intr_regs.mask)];
+	u64 regs[8 * sizeof(sample.intr_regs->mask)];
+	int ret;
 
 	if (intel_pt_skip_event(pt))
 		return 0;
 
+	perf_sample__init(&sample, /*all=*/true);
 	intel_pt_prep_a_sample(ptq, event, &sample);
 
 	sample.id = id;
@@ -2291,15 +2333,16 @@ static int intel_pt_do_synth_pebs_sample(struct intel_pt_queue *ptq, struct evse
 	     items->mask[INTEL_PT_XMM_POS])) {
 		u64 regs_mask = evsel->core.attr.sample_regs_intr;
 		u64 *pos;
+		struct regs_dump *intr_regs = perf_sample__intr_regs(&sample);
 
-		sample.intr_regs.abi = items->is_32_bit ?
+		intr_regs->abi = items->is_32_bit ?
 				       PERF_SAMPLE_REGS_ABI_32 :
 				       PERF_SAMPLE_REGS_ABI_64;
-		sample.intr_regs.regs = regs;
+		intr_regs->regs = regs;
 
-		pos = intel_pt_add_gp_regs(&sample.intr_regs, regs, items, regs_mask);
+		pos = intel_pt_add_gp_regs(intr_regs, regs, items, regs_mask);
 
-		intel_pt_add_xmm(&sample.intr_regs, pos, items, regs_mask);
+		intel_pt_add_xmm(intr_regs, pos, items, regs_mask);
 	}
 
 	if (sample_type & PERF_SAMPLE_BRANCH_STACK) {
@@ -2361,7 +2404,9 @@ static int intel_pt_do_synth_pebs_sample(struct intel_pt_queue *ptq, struct evse
 		sample.transaction = txn;
 	}
 
-	return intel_pt_deliver_synth_event(pt, event, &sample, sample_type);
+	ret = intel_pt_deliver_synth_event(pt, event, &sample, sample_type);
+	perf_sample__exit(&sample);
+	return ret;
 }
 
 static int intel_pt_synth_single_pebs_sample(struct intel_pt_queue *ptq)
@@ -2407,16 +2452,17 @@ static int intel_pt_synth_events_sample(struct intel_pt_queue *ptq)
 {
 	struct intel_pt *pt = ptq->pt;
 	union perf_event *event = ptq->event_buf;
-	struct perf_sample sample = { .ip = 0, };
+	struct perf_sample sample;
 	struct {
 		struct perf_synth_intel_evt cfe;
 		struct perf_synth_intel_evd evd[INTEL_PT_MAX_EVDS];
 	} raw;
-	int i;
+	int i, ret;
 
 	if (intel_pt_skip_event(pt))
 		return 0;
 
+	perf_sample__init(&sample, /*all=*/true);
 	intel_pt_prep_p_sample(pt, ptq, event, &sample);
 
 	sample.id        = ptq->pt->evt_id;
@@ -2438,20 +2484,24 @@ static int intel_pt_synth_events_sample(struct intel_pt_queue *ptq)
 			  ptq->state->evd_cnt * sizeof(struct perf_synth_intel_evd);
 	sample.raw_data = perf_synth__raw_data(&raw);
 
-	return intel_pt_deliver_synth_event(pt, event, &sample,
-					    pt->evt_sample_type);
+	ret = intel_pt_deliver_synth_event(pt, event, &sample,
+					   pt->evt_sample_type);
+	perf_sample__exit(&sample);
+	return ret;
 }
 
 static int intel_pt_synth_iflag_chg_sample(struct intel_pt_queue *ptq)
 {
 	struct intel_pt *pt = ptq->pt;
 	union perf_event *event = ptq->event_buf;
-	struct perf_sample sample = { .ip = 0, };
+	struct perf_sample sample;
 	struct perf_synth_intel_iflag_chg raw;
+	int ret;
 
 	if (intel_pt_skip_event(pt))
 		return 0;
 
+	perf_sample__init(&sample, /*all=*/true);
 	intel_pt_prep_p_sample(pt, ptq, event, &sample);
 
 	sample.id = ptq->pt->iflag_chg_id;
@@ -2471,8 +2521,10 @@ static int intel_pt_synth_iflag_chg_sample(struct intel_pt_queue *ptq)
 	sample.raw_size = perf_synth__raw_size(raw);
 	sample.raw_data = perf_synth__raw_data(&raw);
 
-	return intel_pt_deliver_synth_event(pt, event, &sample,
-					    pt->iflag_chg_sample_type);
+	ret = intel_pt_deliver_synth_event(pt, event, &sample,
+					   pt->iflag_chg_sample_type);
+	perf_sample__exit(&sample);
+	return ret;
 }
 
 static int intel_pt_synth_error(struct intel_pt *pt, int code, int cpu,