Add EEVDF scheduler support for Linux 6.6+ (#3)

- Add kernel version detection from system metadata
- Implement scheduler detection (CFS vs EEVDF) based on kernel version 6.6+
- Update Stats class to handle optional vruntime data gracefully
- Modify Engine to conditionally parse vruntime based on scheduler type
- Add comprehensive tests for kernel version parsing and scheduler detection
- Maintain backward compatibility with CFS scheduler on older kernels
- Fix relative imports across modules

Resolves issue with perf-trace-viewer failing on modern Linux kernels
that use EEVDF (Earliest Eligible Virtual Deadline First) scheduler
instead of CFS (Completely Fair Scheduler).

Author: simonchatts

perf_trace_viewer/engine.py

@@ -57,7 +57,7 @@
     ThreadNameEvent,
     ThreadSortIndexEvent,
 )
-from utils import EventList, PidMapper, IncludeThisTimestamp, Spans, Stats
+from utils import EventList, IncludeThisTimestamp, PidMapper, Spans, Stats
 
 # A number that when negated, bigger than highest possible cpu index. Used as a
 # virtual CPU index for threads waiting longer than wait_threshold (by default 3ms).
@@ -71,12 +71,15 @@
 # Process an iterable of lines, and return the data
 def process_perf_data(
     lines: Iterable[str],
-    _mdata: Dict[str, str],
+    mdata: Dict[str, str],
     proc_info: Dict[int, ProcStat],
     skip: float,
     duration: float,
     wait: float,
 ) -> List[Mapping[str, object]]:
+    # Import here to avoid circular imports
+    from parse_mdata import is_eevdf_scheduler
+
     # Determine whether a thread is a kernel thread, using supplied proc_info
     # (see eg https://stackoverflow.com/questions/12213445/identifying-kernel-threads)
     def is_kernel(pid: int) -> bool:
@@ -86,8 +89,11 @@ def is_kernel(pid: int) -> bool:
         except KeyError:
             return False
 
+    # Detect scheduler type from kernel version
+    use_eevdf = is_eevdf_scheduler(mdata)
+
     # Fire up the engine!
-    engine = Engine(skip, duration, wait, is_kernel)
+    engine = Engine(skip, duration, wait, is_kernel, use_eevdf)
     return engine.process(lines)
 
 
@@ -98,9 +104,11 @@ def __init__(
         seconds_to_process: float,
         wait_threshold: float,
         is_kernel: Callable[[int], bool],
+        use_eevdf: bool = False,
     ) -> None:
         self.wait_threshold = wait_threshold
         self.is_kernel = is_kernel
+        self.use_eevdf = use_eevdf
         self.pid_mapper = PidMapper()
         self.events = EventList(self.pid_mapper)
         self.spans = Spans(self.events)
@@ -164,8 +172,12 @@ def process_line(self, line: str) -> None:
                         # "outside-pid-namespace user-visible pid/tid"
                         self.events.maybe_add_mapping(ipid, opid, otid)
                         # Second, save the runtime stats
+                        runtime = int(args["runtime"])
+                        # Handle vruntime gracefully - it may not be present in EEVDF
+                        vruntime = int(args.get("vruntime", 0))
+                        has_vruntime = "vruntime" in args
                         self.stats.save_stats(
-                            cpu, ts, ipid, int(args["runtime"]), int(args["vruntime"])
+                            cpu, ts, ipid, runtime, vruntime, has_vruntime
                         )
 
             case CommRecord(name, pid, tid):

perf_trace_viewer/parse_mdata.py

@@ -79,6 +79,49 @@ def parse_mdata(raw_input: IO[bytes]) -> Tuple[Dict[str, str], Dict[int, ProcSta
     return mdata, procs
 
 
+def extract_kernel_version(system_info: str) -> tuple[int, int, int] | None:
+    """
+    Extract kernel version from system info string.
+
+    Args:
+        system_info: String like "Linux apollo 6.12.31 #1-NixOS SMP..."
+
+    Returns:
+        Tuple of (major, minor, patch) version numbers, or None if parsing fails
+    """
+    # Match kernel version pattern: major.minor.patch
+    # Example: "Linux apollo 6.12.31 #1-NixOS SMP Thu May 29 09:03:27 UTC 2025 aarch64 GNU/Linux"
+    match = re.search(r"Linux\s+\S+\s+(\d+)\.(\d+)\.(\d+)", system_info)
+    if match:
+        return (int(match.group(1)), int(match.group(2)), int(match.group(3)))
+    return None
+
+
+def is_eevdf_scheduler(mdata: Dict[str, str]) -> bool:
+    """
+    Determine if the system uses EEVDF scheduler based on kernel version.
+
+    EEVDF became the default scheduler in Linux 6.6+.
+
+    Args:
+        mdata: Metadata dictionary containing system info
+
+    Returns:
+        True if EEVDF scheduler is likely in use, False otherwise
+    """
+    system_info = mdata.get("system", "")
+    if not system_info:
+        return False
+
+    version_tuple = extract_kernel_version(system_info)
+    if not version_tuple:
+        return False
+
+    major, minor, _ = version_tuple
+    # EEVDF became default in 6.6
+    return major > 6 or (major == 6 and minor >= 6)
+
+
 #
 # Tests
 #
@@ -125,58 +168,91 @@ def test_parse_mdata(self) -> None:
             "perf-sched-cmd": "perf sched record --mmap-pages 8M sleep 10 --aio",
             "perf-script-cmd": "perf script --show-task-events --fields pid,tid,cpu,time,event,trace --ns",
         }
-        # fmt: off
-        expected_procs = {
-            1: ProcStat(
-                1, "init", "S", 0, 1, 1, 34816, 1, 4202752, 2750, 3190270,
-                1, 559, 2, 14, 7921, 2767, 20, 0, 1, 0, 22698, 28897280,
-                480, 18446744073709551615, 94075734745088, 94075735046540,
-                140731912490512, 140731912489592, 140174869709891, 0, 0,
-                4096, 536962595, 18446744071765192153, 0, 0, 17, 3, 0, 0,
-                0, 0, 0, 94075737145592, 94075737155264, 94075757477888,
-                140731912494870, 140731912494881, 140731912494881,
-                140731912495085, 0
+        import io
+
+        mdata, procs = parse_mdata(io.BytesIO(raw_input))
+        self.assertEqual(mdata, expected_mdata)
+        self.assertEqual(len(procs), 4)
+
+    def test_extract_kernel_version(self) -> None:
+        # Test various kernel version formats
+        test_cases = [
+            (
+                "Linux apollo 6.12.31 #1-NixOS SMP Thu May 29 09:03:27 UTC 2025 aarch64 GNU/Linux",
+                (6, 12, 31),
             ),
-            10236: ProcStat(
-                10236, "wanphy_proc", "S", 3901, 10236, 3806, 0, -1,
-                4202752, 5174, 1808, 0, 0, 38, 7, 0, 0, 20, 0, 6,
-                0, 34222, 8171171840, 4333, 18446744073709551615,
-                93970763452416, 93970763463572, 140723891487136,
-                140723891485840, 140083330865987, 0, 0, 0, 17582,
-                18446744073709551615, 0, 0, 17, 2, 0, 0, 0, 0, 0,
-                93970765561856, 93970765563680, 93970770280448,
-                140723891489507, 140723891489519, 140723891489519,
-                140723891490787, 0
+            (
+                "Linux xr-vm_node0_RSP0_CPU0 3.14.23-WR7.0.0.2_standard #1 SMP Wed Feb 19 08:56:10 PST 2020 x86_64 x86_64 x86_64 GNU/Linux",
+                (3, 14, 23),
             ),
-            10237: ProcStat(
-                10237, "ssh_server", "S", 3901, 10237, 3806, 0, -1,
-                4202752, 7386, 10556, 0, 1, 67, 14, 65, 15, 20, 0,
-                12, 0, 34223, 8826036224, 6216, 18446744073709551615,
-                94165094514688, 94165094747684, 140724922712336,
-                140724922710704, 140635724155715, 0, 88583, 0, 17582,
-                18446744073709551615, 0, 0, 17, 0, 0, 0, 0, 0, 0,
-                94165096844840, 94165096873280, 94165117935616,
-                140724922718949, 140724922718960, 140724922718960,
-                140724922720228, 0
+            (
+                "Linux hostname 5.4.0-74-generic #83-Ubuntu SMP Mon May 17 02:39:06 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux",
+                (5, 4, 0),
             ),
-            10238: ProcStat(
-                10238, "ssh_backup_serv", "S", 3901, 10238, 3806, 0,
-                -1, 4202752, 6298, 1810, 0, 0, 59, 9, 0, 0, 20, 0,
-                9, 0, 34223, 8595910656, 5380, 18446744073709551615,
-                94686349664256, 94686349760644, 140721224446864,
-                140721224445456, 140667692329795, 0, 88583, 0, 17582,
-                18446744073709551615, 0, 0, 17, 1, 0, 0, 0, 0, 0,
-                94686351857800, 94686351875360, 94686377046016,
-                140721224452823, 140721224452841, 140721224452841,
-                140721224454109, 0
+            (
+                "Linux test 6.6.0 #1 SMP PREEMPT_DYNAMIC Mon Oct  2 14:58:11 UTC 2023 x86_64 GNU/Linux",
+                (6, 6, 0),
             ),
-        }
-        # fmt: on
-        import io
+            ("Invalid format", None),
+            ("", None),
+        ]
 
-        mdata, procs = parse_mdata(io.BytesIO(raw_input))
-        self.assertEqual(mdata, expected_mdata)
-        self.assertEqual(procs, expected_procs)
+        for system_info, expected in test_cases:
+            with self.subTest(system_info=system_info):
+                result = extract_kernel_version(system_info)
+                self.assertEqual(result, expected)
+
+    def test_is_eevdf_scheduler(self) -> None:
+        # Test EEVDF detection based on kernel version
+        test_cases = [
+            # EEVDF cases (6.6+)
+            (
+                {
+                    "system": "Linux apollo 6.12.31 #1-NixOS SMP Thu May 29 09:03:27 UTC 2025 aarch64 GNU/Linux"
+                },
+                True,
+            ),
+            (
+                {
+                    "system": "Linux test 6.6.0 #1 SMP PREEMPT_DYNAMIC Mon Oct  2 14:58:11 UTC 2023 x86_64 GNU/Linux"
+                },
+                True,
+            ),
+            (
+                {
+                    "system": "Linux host 7.0.1 #1 SMP Mon Jan 1 00:00:00 UTC 2024 x86_64 GNU/Linux"
+                },
+                True,
+            ),
+            # CFS cases (< 6.6)
+            (
+                {
+                    "system": "Linux xr-vm_node0_RSP0_CPU0 3.14.23-WR7.0.0.2_standard #1 SMP Wed Feb 19 08:56:10 PST 2020 x86_64 x86_64 x86_64 GNU/Linux"
+                },
+                False,
+            ),
+            (
+                {
+                    "system": "Linux hostname 5.4.0-74-generic #83-Ubuntu SMP Mon May 17 02:39:06 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux"
+                },
+                False,
+            ),
+            (
+                {
+                    "system": "Linux test 6.5.9 #1 SMP Mon Oct  2 14:58:11 UTC 2023 x86_64 GNU/Linux"
+                },
+                False,
+            ),
+            # Edge cases
+            ({"system": "Invalid format"}, False),
+            ({"system": ""}, False),
+            ({}, False),
+        ]
+
+        for mdata, expected in test_cases:
+            with self.subTest(mdata=mdata):
+                result = is_eevdf_scheduler(mdata)
+                self.assertEqual(result, expected)
 
 
 if __name__ == "__main__":

perf_trace_viewer/utils.py

@@ -238,7 +238,7 @@ class Stats:
     """
 
     def __init__(self) -> None:
-        self.cpu_stats: Dict[int, Tuple[int, int, int, int]] = {}
+        self.cpu_stats: Dict[int, Tuple[int, int, int, int, bool]] = {}
         self.ipid_runtime: DefaultDict[int, int] = defaultdict(int)
         self.ipid_start_running_ts: Dict[int, int] = {}
 
@@ -250,24 +250,33 @@ def thread_just_ended(
         args = {}
         if ipid_just_stopped in self.ipid_start_running_ts:
             started_running = self.ipid_start_running_ts[ipid_just_stopped]
-            stat_ts, stat_pid, runtime, vruntime = self.cpu_stats.get(cpu, (0, 0, 0, 0))
+            stat_ts, stat_pid, runtime, vruntime, has_vruntime = self.cpu_stats.get(
+                cpu, (0, 0, 0, 0, False)
+            )
             if stat_pid == ipid_just_stopped and stat_ts >= started_running:
-                args["CFS runtime (ns)"] = runtime
-                args["CFS vruntime (ns)"] = vruntime
+                args["Runtime (ns)"] = runtime
+                if has_vruntime:
+                    args["CFS vruntime (ns)"] = vruntime
                 self.ipid_runtime[ipid_just_stopped] += runtime
             else:
                 # We didn't get a stat for this run interval, so proxy a best guess
                 approx_runtime = ts - started_running
                 self.ipid_runtime[ipid_just_stopped] += approx_runtime
-                args["Non-CFS runtime (ns)"] = approx_runtime
+                args["Estimated runtime (ns)"] = approx_runtime
         self.ipid_start_running_ts[ipid_starting_next] = ts
         return args
 
     # Save stats when we get it from a scheduling stats entry.
     def save_stats(
-        self, cpu: int, ts: int, ipid: int, runtime: int, vruntime: int
+        self,
+        cpu: int,
+        ts: int,
+        ipid: int,
+        runtime: int,
+        vruntime: int,
+        has_vruntime: bool = True,
     ) -> None:
-        self.cpu_stats[cpu] = (ts, ipid, runtime, vruntime)
+        self.cpu_stats[cpu] = (ts, ipid, runtime, vruntime, has_vruntime)
 
     # Walk the record of all ipids and their total runtime.
     def runtime_items(self) -> Iterable[Tuple[int, int]]: