backtraces/
backtraces.rs

1//! Per-call-site report demo.
2//!
3//! Run with:
4//!   cargo run --release --features backtraces --example backtraces
5//!
6//! Requires frame pointers for useful output. The in-crate
7//! `.cargo/config.toml` enables `-C force-frame-pointers=yes` for
8//! this crate's own builds; downstream users opting into the
9//! `backtraces` feature must enable the flag in their own build.
10
11#[cfg(feature = "backtraces")]
12#[global_allocator]
13static GLOBAL: mod_alloc::ModAlloc = mod_alloc::ModAlloc::new();
14
15#[cfg(feature = "backtraces")]
16#[inline(never)]
17fn alloc_small() {
18    let v: Vec<u8> = Vec::with_capacity(64);
19    std::hint::black_box(&v);
20}
21
22#[cfg(feature = "backtraces")]
23#[inline(never)]
24fn alloc_medium() {
25    let v: Vec<u8> = Vec::with_capacity(1024);
26    std::hint::black_box(&v);
27}
28
29#[cfg(feature = "backtraces")]
30#[inline(never)]
31fn alloc_large() {
32    let v: Vec<u8> = Vec::with_capacity(64 * 1024);
33    std::hint::black_box(&v);
34}
35
36#[cfg(feature = "backtraces")]
37fn main() {
38    for _ in 0..1_000 {
39        alloc_small();
40    }
41    for _ in 0..100 {
42        alloc_medium();
43    }
44    for _ in 0..10 {
45        alloc_large();
46    }
47
48    let snap = GLOBAL.snapshot();
49    println!("Process-wide snapshot:");
50    println!("  alloc_count:   {}", snap.alloc_count);
51    println!("  total_bytes:   {}", snap.total_bytes);
52    println!("  current_bytes: {}", snap.current_bytes);
53    println!("  peak_bytes:    {}", snap.peak_bytes);
54    println!();
55
56    let mut sites = GLOBAL.call_sites();
57    sites.sort_by_key(|s| std::cmp::Reverse(s.total_bytes));
58
59    println!("Top 10 call sites by total bytes:");
60    println!(
61        "{:>10}  {:>14}  {:>4}  {:>18}",
62        "count", "total_bytes", "frm", "top frame"
63    );
64    for (rank, site) in sites.iter().take(10).enumerate() {
65        println!(
66            "{rank:>2}: {count:>6}  {bytes:>14}  {frm:>4}  {top:#018x}",
67            rank = rank,
68            count = site.count,
69            bytes = site.total_bytes,
70            frm = site.frame_count,
71            top = site.frames[0],
72        );
73    }
74}
75
76#[cfg(not(feature = "backtraces"))]
77fn main() {
78    eprintln!(
79        "this example requires the `backtraces` feature; run with \
80         `cargo run --features backtraces --example backtraces`"
81    );
82}
backtraces/backtraces.rs

backtraces/
backtraces.rs
