Documentation
¶
Overview ¶
Package timesync provides time conversion utilities for converting kernel boot-clock timestamps from eBPF events to wall-clock time.
eBPF events are stamped with bpf_ktime_get_boot_ns() (CLOCK_BOOTTIME): nanoseconds since system boot, including time spent suspended. This package converts them to absolute wall-clock time by adding the boot instant, which it derives from a paired CLOCK_REALTIME/CLOCK_BOOTTIME reading (falling back to /proc/stat btime).
CLOCK_BOOTTIME rather than CLOCK_MONOTONIC is deliberate: CLOCK_MONOTONIC freezes across suspend, which would drift these spans behind the wall-clock (CLOCK_REALTIME) root span by the host's cumulative suspend time.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Converter ¶
type Converter struct {
// contains filtered or unexported fields
}
Converter handles conversion from kernel boot-clock timestamps to wall-clock time.
eBPF events are stamped with bpf_ktime_get_boot_ns() (CLOCK_BOOTTIME): nanoseconds since boot, INCLUDING time spent suspended. We reconstruct wall-clock as bootTime + boottime_ns, where bootTime is the wall-clock instant of boot.
The distinction from CLOCK_MONOTONIC matters: CLOCK_MONOTONIC freezes across suspend, so btime + monotonic_ns drifts behind real wall-clock by the host's cumulative suspend time. That desynced these spans from the process.tree root span (stamped with the userspace CLOCK_REALTIME clock) and inflated the rendered trace duration by hours on any machine that had suspended.
func NewConverter ¶
NewConverter creates a new time converter.
Primary path: anchor on a paired reading of CLOCK_REALTIME and CLOCK_BOOTTIME captured together, so bootTime = realtimeNow - boottimeElapsed. This is sub-second accurate, tracks any NTP adjustments to realtime since boot (which keeps us consistent with the time.Now() used for the root span), and needs no /proc parsing.
Fallback: /proc/stat btime (integer-second boot wall time). This is still correct for CLOCK_BOOTTIME-domain events (btime + boottime_ns ≈ realtime), just coarser. Last resort is a conservative estimate.
func (*Converter) BootNanosToWallClock ¶ added in v0.8.12
BootNanosToWallClock converts a CLOCK_BOOTTIME timestamp (nanoseconds since boot, including suspend) to wall-clock time. Pure function over the boot time captured at initialization.
Source Files