cerc-io/lighthouse
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Enable mallinfo2 behind feature flag (#2864)

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## Proposed Changes

Add `mallinfo2` behind a feature flag so that we can get accurate memory metrics during debugging. It can be enabled when building Lighthouse like so (so long as the platform supports it):

```
cargo install --path lighthouse --features "malloc_utils/mallinfo2"
```
This commit is contained in:
Michael Sproul 2021-12-15 20:39:50 +00:00
parent 4dcb262c2d
commit 10dac51c6f
2 changed files with 32 additions and 19 deletions
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3
common/malloc_utils/Cargo.toml
View File

@ -11,3 +11,6 @@ lighthouse_metrics = { path = "../lighthouse_metrics" }
lazy_static = "1.4.0"
libc = "0.2.79"
parking_lot = "0.11.0"
[features]
mallinfo2 = []

48
common/malloc_utils/src/glibc.rs
View File

@ -82,27 +82,8 @@ lazy_static! {
/// Calls `mallinfo` and updates Prometheus metrics with the results.
pub fn scrape_mallinfo_metrics() {
// The docs for this function say it is thread-unsafe since it may return inconsistent results.
// Since these are just metrics it's not a concern to us if they're sometimes inconsistent.
//
// There exists a `mallinfo2` function, however it was released in February 2021 and this seems
// too recent to rely on.
//
// Docs:
//
// https://man7.org/linux/man-pages/man3/mallinfo.3.html
let mallinfo = mallinfo();
/// Cast a C integer as returned by `mallinfo` to an unsigned i64.
///
/// A cast from `i32` to `i64` preserves the sign bit, resulting in incorrect negative values.
/// Going via `u32` treats the sign bit as part of the number.
///
/// Results are still wrong for memory usage over 4GiB due to limitations of mallinfo.
fn unsigned_i64(x: i32) -> i64 {
x as u32 as i64
}
set_gauge(&MALLINFO_ARENA, unsigned_i64(mallinfo.arena));
set_gauge(&MALLINFO_ORDBLKS, unsigned_i64(mallinfo.ordblks));
set_gauge(&MALLINFO_SMBLKS, unsigned_i64(mallinfo.smblks));
@ -114,6 +95,23 @@ pub fn scrape_mallinfo_metrics() {
set_gauge(&MALLINFO_KEEPCOST, unsigned_i64(mallinfo.keepcost));
}
/// Cast a C integer as returned by `mallinfo` to an unsigned i64.
///
/// A cast from `i32` to `i64` preserves the sign bit, resulting in incorrect negative values.
/// Going via `u32` treats the sign bit as part of the number.
///
/// Results are still wrong for memory usage over 4GiB due to limitations of mallinfo.
#[cfg(not(feature = "mallinfo2"))]
fn unsigned_i64(x: i32) -> i64 {
x as u32 as i64
}
/// Cast a C `size_t` as returned by `mallinfo2` to an unsigned i64.
#[cfg(feature = "mallinfo2")]
fn unsigned_i64(x: usize) -> i64 {
x as i64
}
/// Perform all configuration routines.
pub fn configure_glibc_malloc() -> Result<(), String> {
if !env_var_present(ENV_VAR_MMAP_THRESHOLD) {
@ -146,12 +144,24 @@ fn mallopt(param: c_int, val: c_int) -> c_int {
unsafe { libc::mallopt(param, val) }
}
/// By default we use `mallinfo`, but it overflows, so `mallinfo2` should be enabled if available.
///
/// https://man7.org/linux/man-pages/man3/mallinfo.3.html
#[cfg(not(feature = "mallinfo2"))]
fn mallinfo() -> libc::mallinfo {
// Prevent this function from being called in parallel with any other non-thread-safe function.
let _lock = GLOBAL_LOCK.lock();
unsafe { libc::mallinfo() }
}
/// Use `mallinfo2` if enabled.
#[cfg(feature = "mallinfo2")]
fn mallinfo() -> libc::mallinfo2 {
// Prevent this function from being called in parallel with any other non-thread-safe function.
let _lock = GLOBAL_LOCK.lock();
unsafe { libc::mallinfo2() }
}
fn into_result(result: c_int) -> Result<(), c_int> {
if result == 1 {
Ok(())