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Metrics

Cross-platform system metrics: load average, memory, CPU time, and process RSS. Single call, no configuration, no external dependencies.

Why Metrics?

Modula-2 has no built-in access to OS-level performance counters. Metrics provides a single Snapshot call that fills a record with nine system measurements, backed by platform-specific C code (macOS via Mach/sysctl, Linux via sysinfo/procfs). No initialization, no cleanup -- just call and read.

Used by pdc (Performance Data Collector) and any application that needs system telemetry.

Types

SysSnapshot

TYPE
  SysSnapshot = RECORD
    load1:      LONGINT;   (* 1-min load avg x 1000  *)
    load5:      LONGINT;   (* 5-min load avg x 1000  *)
    load15:     LONGINT;   (* 15-min load avg x 1000 *)
    memTotalMB: LONGINT;   (* total physical RAM (MB) *)
    memFreeMB:  LONGINT;   (* free + inactive RAM (MB) *)
    cpuUserUs:  LONGINT;   (* user CPU time (us)      *)
    cpuSysUs:   LONGINT;   (* system CPU time (us)    *)
    rssKB:      LONGINT;   (* current RSS (KB)        *)
    maxRssKB:   LONGINT;   (* peak RSS (KB)           *)
  END;

All fields are LONGINT (signed 64-bit). Load averages are multiplied by 1000 to preserve three decimal places without floating point. CPU times are cumulative microseconds since process start.

Field Source (macOS) Source (Linux)
load1/5/15 getloadavg() getloadavg()
memTotalMB sysctl(HW_MEMSIZE) sysinfo.totalram
memFreeMB Mach host_statistics64 (free + inactive) sysinfo.freeram + bufferram
cpuUserUs getrusage(RUSAGE_SELF) getrusage(RUSAGE_SELF)
cpuSysUs getrusage(RUSAGE_SELF) getrusage(RUSAGE_SELF)
rssKB Mach task_info /proc/self/status VmRSS
maxRssKB getrusage (bytes/1024) getrusage (already KB)

Procedures

  • PROCEDURE Snapshot(VAR snap: SysSnapshot) Fill snap with current system metrics. All nine fields are populated in a single call. Fields that cannot be read on the current platform are left as zero.

Example

FROM Metrics IMPORT SysSnapshot, Snapshot;
FROM InOut IMPORT WriteString, WriteLn, WriteInt;

VAR snap: SysSnapshot;

BEGIN
  Snapshot(snap);
  WriteString("load1="); WriteInt(snap.load1, 1); WriteLn;
  WriteString("rssKB="); WriteInt(snap.rssKB, 1); WriteLn;
  WriteString("memFreeMB="); WriteInt(snap.memFreeMB, 1); WriteLn
END

Architecture

Metrics.def          High-level Modula-2 API (SysSnapshot, Snapshot)
  |
Metrics.mod          Delegates to FFI bridge via ADR(snap)
  |
MetricsBridge.def    FOR "C" declaration (ADDRESS-based FFI)
  |
metrics_bridge.c     Platform-specific C: getloadavg, sysctl/sysinfo, getrusage

No external library dependency. The C bridge uses only POSIX and OS headers.