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Merged
not-matthias merged 2 commits into from
Oct 1, 2026
Merged

perf(memtrack): stop capturing stacks on free #558

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26d6580
perf(memtrack): stop capturing stacks on free
not-matthias Sep 30, 2026
c01f5d2
refactor(memtrack): drop stack_hash from Free events
not-matthias Oct 1, 2026
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5 changes: 3 additions & 2 deletions crates/memtrack/src/ebpf/c/allocator.h
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Original file line number Diff line number Diff line change
Expand Up @@ -27,14 +27,15 @@
submit_block; \
}

/* free() carries no stack: the flamegraph only attributes allocations, so a
* copy here would double the capture cost for nothing. */
#define UPROBE_RET(name, arg_expr, submit_block) \
SEC(UPROBE_SEC) \
int uprobe_##name(struct pt_regs* ctx) { \
__u64 arg0 = arg_expr; \
if (arg0 == 0) { \
return 0; \
} \
__u64 stack_hash = capture_stack(ctx); \
submit_block; \
}

Expand Down Expand Up @@ -86,7 +87,7 @@
UPROBE_ARG_RET(malloc, PT_REGS_PARM1(ctx),
{ return submit_alloc_event(arg0, ret_val, stack_hash); })

UPROBE_RET(free, PT_REGS_PARM1(ctx), { return submit_free_event(arg0, stack_hash); })
UPROBE_RET(free, PT_REGS_PARM1(ctx), { return submit_free_event(arg0); })

UPROBE_ARG_RET(calloc, PT_REGS_PARM1(ctx) * PT_REGS_PARM2(ctx),
{ return submit_calloc_event(arg0, ret_val, stack_hash); })
Expand Down
3 changes: 1 addition & 2 deletions crates/memtrack/src/ebpf/c/event.h
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Expand Up @@ -74,8 +74,7 @@ struct event {

/* Deallocation event (free) */
struct {
uint64_t addr; /* address to free */
uint64_t stack_hash; /* caller stack identity; 0 = not captured */
uint64_t addr; /* address to free */
} free;

/* Reallocation event - includes both old and new addresses */
Expand Down
7 changes: 2 additions & 5 deletions crates/memtrack/src/ebpf/c/utils/event_helpers.h
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Expand Up @@ -113,11 +113,8 @@ static __always_inline int submit_calloc_event(__u64 size, __u64 addr, __u64 sta
});
}

static __always_inline int submit_free_event(__u64 addr, __u64 stack_hash) {
SUBMIT_GATED_EVENT(EVENT_TYPE_FREE, {
e->data.free.addr = addr;
e->data.free.stack_hash = stack_hash;
});
static __always_inline int submit_free_event(__u64 addr) {
SUBMIT_GATED_EVENT(EVENT_TYPE_FREE, { e->data.free.addr = addr; });
}

static __always_inline int submit_realloc_event(__u64 old_addr, __u64 new_addr, __u64 size,
Expand Down
7 changes: 1 addition & 6 deletions crates/memtrack/src/ebpf/events.rs
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Expand Up @@ -39,12 +39,7 @@ pub fn parse_event(data: &[u8]) -> Option<MemtrackEvent> {
stack_hash: event.data.alloc.stack_hash,
},
),
EVENT_TYPE_FREE => (
event.data.free.addr,
MemtrackEventKind::Free {
stack_hash: event.data.free.stack_hash,
},
),
EVENT_TYPE_FREE => (event.data.free.addr, MemtrackEventKind::Free),
EVENT_TYPE_CALLOC => (
event.data.alloc.addr,
MemtrackEventKind::Calloc {
Expand Down
2 changes: 1 addition & 1 deletion crates/memtrack/tests/c_tests.rs
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Expand Up @@ -106,7 +106,7 @@ fn test_track_allocators_disabled_skips_allocations() -> Result<(), Box<dyn std:
matches!(
e.kind,
MemtrackEventKind::Malloc { .. }
| MemtrackEventKind::Free { .. }
| MemtrackEventKind::Free
| MemtrackEventKind::Calloc { .. }
| MemtrackEventKind::Realloc { .. }
| MemtrackEventKind::AlignedAlloc { .. }
Expand Down
3 changes: 1 addition & 2 deletions crates/memtrack/tests/dlopen_tests.rs
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Expand Up @@ -78,8 +78,7 @@ fn test_dlopen_allocator() -> Result<(), Box<dyn std::error::Error>> {
let free_count = events
.iter()
.filter(|e| {
matches!(e.kind, MemtrackEventKind::Free { .. })
&& malloc_addrs.contains(&e.addr)
matches!(e.kind, MemtrackEventKind::Free) && malloc_addrs.contains(&e.addr)
})
.count();

Expand Down
6 changes: 3 additions & 3 deletions crates/memtrack/tests/shared.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ macro_rules! assert_events_snapshot {
matches!(
e.kind,
MemtrackEventKind::Malloc { .. }
| MemtrackEventKind::Free { .. }
| MemtrackEventKind::Free
| MemtrackEventKind::Calloc { .. }
| MemtrackEventKind::Realloc { .. }
| MemtrackEventKind::AlignedAlloc { .. }
Expand Down Expand Up @@ -97,7 +97,7 @@ macro_rules! assert_events_with_marker_for_each_variant {
/// differ between runs of the same workload.
pub fn describe_kind(kind: &MemtrackEventKind) -> String {
match kind {
MemtrackEventKind::Free { .. } => "Free".to_string(),
MemtrackEventKind::Free => "Free".to_string(),
MemtrackEventKind::Malloc { size, .. } => format!("Malloc {{ size: {size} }}"),
MemtrackEventKind::Calloc { size, .. } => format!("Calloc {{ size: {size} }}"),
MemtrackEventKind::AlignedAlloc { size, .. } => format!("AlignedAlloc {{ size: {size} }}"),
Expand Down Expand Up @@ -280,7 +280,7 @@ fn event_profile(events: &[Event]) -> EventProfile {
// Only allocator events are comparable across variants: RSS and
// lifecycle values (sizes, pids) are per-run.
match event.kind {
MemtrackEventKind::Free { .. } => {
MemtrackEventKind::Free => {
if !live.remove(&event.addr) {
continue;
}
Expand Down
6 changes: 3 additions & 3 deletions crates/memtrack/tests/snapshots/stack_tests__nested_doubling.snap
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Expand Up @@ -6,7 +6,7 @@ expression: format_events(&events)
"Malloc { size: 1024, has_stack: true }",
"Malloc { size: 2048, has_stack: true }",
"Malloc { size: 4096, has_stack: true }",
"Free { has_stack: true }",
"Free { has_stack: true }",
"Free { has_stack: true }",
"Free",
"Free",
"Free",
]
6 changes: 3 additions & 3 deletions crates/memtrack/tests/snapshots/stack_tests__nested_doubling_shared_free.snap
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Expand Up @@ -6,7 +6,7 @@ expression: format_events(&events)
"Malloc { size: 1024, has_stack: true }",
"Malloc { size: 2048, has_stack: true }",
"Malloc { size: 4096, has_stack: true }",
"Free { has_stack: true }",
"Free { has_stack: true }",
"Free { has_stack: true }",
"Free",
"Free",
"Free",
]
6 changes: 3 additions & 3 deletions ...rack/tests/snapshots/stack_tests__nested_doubling_shared_free_stack_capture_disabled.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ expression: format_events(&events)
"Malloc { size: 1024, has_stack: false }",
"Malloc { size: 2048, has_stack: false }",
"Malloc { size: 4096, has_stack: false }",
"Free { has_stack: false }",
"Free { has_stack: false }",
"Free { has_stack: false }",
"Free",
"Free",
"Free",
]
6 changes: 3 additions & 3 deletions crates/memtrack/tests/snapshots/stack_tests__nested_doubling_stack_capture_disabled.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ expression: format_events(&events)
"Malloc { size: 1024, has_stack: false }",
"Malloc { size: 2048, has_stack: false }",
"Malloc { size: 4096, has_stack: false }",
"Free { has_stack: false }",
"Free { has_stack: false }",
"Free { has_stack: false }",
"Free",
"Free",
"Free",
]
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