1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
// Copyright Materialize, Inc. and contributors. All rights reserved.
//
// Use of this software is governed by the Business Source License
// included in the LICENSE file.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0.

//! Various profiling utilities:
//!
//! (1) Turn jemalloc profiling on and off, and dump heap profiles (`PROF_CTL`)
//! (2) Parse jemalloc heap files and make them into a hierarchical format (`parse_jeheap` and `collate_stacks`)

use std::os::unix::ffi::OsStrExt;
use std::sync::Arc;
use std::{ffi::CString, io::BufRead, time::Instant};
use tokio::sync::Mutex;

use anyhow::bail;
use once_cell::sync::Lazy;
use tempfile::NamedTempFile;
use tikv_jemalloc_ctl::{epoch, raw, stats};

use super::{ProfStartTime, StackProfile, WeightedStack};

#[allow(non_upper_case_globals)]
#[export_name = "malloc_conf"]
pub static malloc_conf: &[u8] = b"prof:true,prof_active:false\0";

pub static PROF_CTL: Lazy<Option<Arc<Mutex<JemallocProfCtl>>>> = Lazy::new(|| {
    if let Some(ctl) = JemallocProfCtl::get() {
        Some(Arc::new(Mutex::new(ctl)))
    } else {
        None
    }
});

#[derive(Copy, Clone, Debug)]
pub struct JemallocProfMetadata {
    pub start_time: Option<ProfStartTime>,
}

#[derive(Debug)]
// Per-process singleton object allowing control of jemalloc profiling facilities.
pub struct JemallocProfCtl {
    md: JemallocProfMetadata,
}

/// Parse a jemalloc profile file, producing a vector of stack traces along with their weights.
pub fn parse_jeheap<R: BufRead>(r: R) -> anyhow::Result<StackProfile> {
    let mut cur_stack = None;
    let mut profile = <StackProfile as Default>::default();
    let mut lines = r.lines();
    let first_line = match lines.next() {
        Some(s) => s,
        None => bail!("Heap dump file was empty"),
    }?;
    // The first line of the file should be e.g. "heap_v2/524288", where the trailing
    // number is the inverse probability of a byte being sampled.
    let sampling_rate = str::parse::<usize>(first_line.trim_start_matches("heap_v2/"))? as f64;
    for line in lines {
        let line = line?;
        let line = line.trim();
        let words = line.split_ascii_whitespace().collect::<Vec<_>>();
        if words.len() > 0 && words[0] == "@" {
            if cur_stack.is_some() {
                bail!("Stack without corresponding weight!")
            }
            let mut addrs = words[1..]
                .iter()
                .map(|w| {
                    let raw = w.trim_start_matches("0x");
                    usize::from_str_radix(raw, 16)
                })
                .collect::<Result<Vec<_>, _>>()?;
            addrs.reverse();
            cur_stack = Some(addrs);
        }
        if words.len() > 2 && words[0] == "t*:" {
            if let Some(addrs) = cur_stack.take() {
                // The format here is e.g.:
                // t*: 40274: 2822125696 [0: 0]
                //
                // "t*" means summary across all threads; someday we will support per-thread dumps but don't now.
                // "40274" is the number of sampled allocations (`n_objs` here).
                // On all released versions of jemalloc, "2822125696" is the total number of bytes in those allocations.
                //
                // To get the predicted number of total bytes from the sample, we need to un-bias it by following the logic in
                // jeprof's `AdjustSamples`: https://github.com/jemalloc/jemalloc/blob/498f47e1ec83431426cdff256c23eceade41b4ef/bin/jeprof.in#L4064-L4074
                //
                // However, this algorithm is actually wrong: you actually need to unbias each sample _before_ you add them together, rather
                // than adding them together first and then unbiasing the average allocation size. But the heap profile format in released versions of jemalloc
                // does not give us access to each individual allocation, so this is the best we can do (and `jeprof` does the same).
                //
                // It usually seems to be at least close enough to being correct to be useful, but could be very wrong if for the same stack, there is a
                // very large amount of variance in the amount of bytes allocated (e.g., if there is one allocation of 8 MB and 1,000,000 of 8 bytes)
                //
                // In the latest unreleased jemalloc sources from github, the issue is worked around by unbiasing the numbers for each sampled allocation,
                // and then fudging them to maintain compatibility with jeprof's logic. So, once those are released and we start using them,
                // this will become even more correct.
                //
                // For more details, see this doc: https://github.com/jemalloc/jemalloc/pull/1902
                //
                // And this gitter conversation between me (Brennan Vincent) and David Goldblatt: https://gitter.im/jemalloc/jemalloc?at=5f31b673811d3571b3bb9b6b
                let n_objs = str::parse::<usize>(words[1].trim_end_matches(':'))? as f64;
                let bytes_in_sampled_objs = str::parse::<usize>(words[2])? as f64;
                let ratio = (bytes_in_sampled_objs / n_objs) / sampling_rate;
                let scale_factor = 1.0 / (1.0 - (-ratio).exp());
                let weight = bytes_in_sampled_objs * scale_factor;
                profile.push(WeightedStack { addrs, weight }, None);
            }
        }
    }
    if cur_stack.is_some() {
        bail!("Stack without corresponding weight!")
    }
    Ok(profile)
}

// See stats.{allocated, active, ...} in http://jemalloc.net/jemalloc.3.html for details
pub struct JemallocStats {
    pub active: usize,
    pub allocated: usize,
    pub metadata: usize,
    pub resident: usize,
    pub retained: usize,
}

impl JemallocProfCtl {
    // Creates and returns the global singleton.
    fn get() -> Option<Self> {
        // SAFETY: "opt.prof" is documented as being readable and returning a bool:
        // http://jemalloc.net/jemalloc.3.html#opt.prof
        let prof_enabled: bool = unsafe { raw::read(b"opt.prof\0") }.unwrap();
        if prof_enabled {
            // SAFETY: "opt.prof_active" is documented as being readable and returning a bool:
            // http://jemalloc.net/jemalloc.3.html#opt.prof_active
            let prof_active: bool = unsafe { raw::read(b"opt.prof_active\0") }.unwrap();
            let start_time = if prof_active {
                Some(ProfStartTime::TimeImmemorial)
            } else {
                None
            };
            let md = JemallocProfMetadata { start_time };
            Some(Self { md })
        } else {
            None
        }
    }

    pub fn get_md(&self) -> JemallocProfMetadata {
        self.md
    }

    pub fn activate(&mut self) -> Result<(), tikv_jemalloc_ctl::Error> {
        // SAFETY: "prof.active" is documented as being writable and taking a bool:
        // http://jemalloc.net/jemalloc.3.html#prof.active
        unsafe { raw::write(b"prof.active\0", true) }?;
        if self.md.start_time.is_none() {
            self.md.start_time = Some(ProfStartTime::Instant(Instant::now()));
        }
        Ok(())
    }

    pub fn deactivate(&mut self) -> Result<(), tikv_jemalloc_ctl::Error> {
        // SAFETY: "prof.active" is documented as being writable and taking a bool:
        // http://jemalloc.net/jemalloc.3.html#prof.active
        unsafe { raw::write(b"prof.active\0", false) }?;
        self.md.start_time = None;
        Ok(())
    }

    pub fn dump(&mut self) -> anyhow::Result<std::fs::File> {
        let f = NamedTempFile::new()?;
        let path = CString::new(f.path().as_os_str().as_bytes().to_vec()).unwrap();

        // SAFETY: "prof.dump" is documented as being writable and taking a C string as input:
        // http://jemalloc.net/jemalloc.3.html#prof.dump
        unsafe { raw::write(b"prof.dump\0", path.as_ptr()) }?;
        Ok(f.into_file())
    }

    pub fn dump_stats(&mut self, json_format: bool) -> anyhow::Result<String> {
        // Try to avoid allocations within `stats_print`
        let mut buf = Vec::with_capacity(1 << 22);
        let mut options = tikv_jemalloc_ctl::stats_print::Options::default();
        options.json_format = json_format;
        tikv_jemalloc_ctl::stats_print::stats_print(&mut buf, options)?;
        Ok(String::from_utf8(buf)?)
    }

    pub fn stats(&self) -> anyhow::Result<JemallocStats> {
        epoch::advance()?;
        Ok(JemallocStats {
            active: stats::active::read()?,
            allocated: stats::allocated::read()?,
            metadata: stats::metadata::read()?,
            resident: stats::resident::read()?,
            retained: stats::retained::read()?,
        })
    }
}