diff options
Diffstat (limited to 'tools/guest-diag')
| -rw-r--r-- | tools/guest-diag/guest_pin_stream.py | 63 |
1 files changed, 46 insertions, 17 deletions
diff --git a/tools/guest-diag/guest_pin_stream.py b/tools/guest-diag/guest_pin_stream.py index f89ed4a..f0f07d8 100644 --- a/tools/guest-diag/guest_pin_stream.py +++ b/tools/guest-diag/guest_pin_stream.py @@ -60,21 +60,32 @@ VMA_PATHS = tuple(p for p in os.environ.get( TRACE = ("/sys/kernel/tracing/trace" if os.path.exists("/sys/kernel/tracing/trace") else "/sys/kernel/debug/tracing/trace") +TRACE_PIPE = ("/sys/kernel/tracing/trace_pipe" + if os.path.exists("/sys/kernel/tracing/trace_pipe") + else "/sys/kernel/debug/tracing/trace_pipe") SEM_EVERY = int(os.environ.get("STREAM_SEM_EVERY", "4")) -class TraceReader: - """Tail the guest trace for new uvmt sems / uvbp pushbuffers in a thread. +def clear_trace(): + """Drop stale ring events so the fallback tail reader cannot re-learn a + previous client's freed sems after a client switch. The new client's + events are delivered fresh through the consuming trace_pipe reader.""" + try: + with open(TRACE, "w") as f: + f.write("") + except OSError: + pass - Reading the trace can block for seconds under client load; doing it in - the scan loop delayed the first GR-window delta (observed a 3 s gap - right when the client's channels appeared). The thread appends to a - queue the main loop drains without blocking. - Push-buffer kptrs are emitted as soon as the client begins its first - push: the host resolves them through the UVM chain and pins the pages, - which is what makes the first CE channel's releases applicable without - waiting for the content sweep. +class TraceReader: + """Stream uvmt sems / uvbp pushbuffers from the guest trace via trace_pipe. + + trace_pipe is a consuming stream: every event is delivered exactly once, + with no ring-window race. The old tail-of-trace reader polled the last + 256 KB every 0.3 s, so a one-shot sem= event could age out of the window + when the client's spin flooded the ring before the next poll - that is + the second-client stall class (the previous client's freed sem was + re-learned from the stale ring while the new client's sem was missed). """ def __init__(self): @@ -82,29 +93,46 @@ class TraceReader: self.seen = set() self.lock = threading.Lock() self.stop = False + self.fd = None self.t = threading.Thread(target=self._run, daemon=True) self.t.start() + def _open(self): + try: + self.fd = os.open(TRACE_PIPE, os.O_RDONLY) + except OSError: + self.fd = None + def _run(self): while not self.stop: + if self.fd is None: + self._open() + if self.fd is None: + time.sleep(1) + continue try: - out = subprocess.run(["tail", "-c", "262144", TRACE], - capture_output=True, timeout=10).stdout - except Exception: - time.sleep(1) + data = os.read(self.fd, 65536) + except OSError: + try: + os.close(self.fd) + except OSError: + pass + self.fd = None + time.sleep(0.5) + continue + if not data: continue with self.lock: - for m in re.finditer(rb"sem=0x([0-9a-fA-F]+)", out): + for m in re.finditer(rb"sem=0x([0-9a-fA-F]+)", data): v = int(m.group(1), 16) if ("s", v) not in self.seen: self.seen.add(("s", v)) self.lines.append("#sem 0x%x\n" % v) - for m in re.finditer(rb"pb=0x([0-9a-fA-F]+)", out): + for m in re.finditer(rb"pb=0x([0-9a-fA-F]+)", data): v = int(m.group(1), 16) if ("p", v) not in self.seen: self.seen.add(("p", v)) self.lines.append("#pb 0x%x\n" % v) - time.sleep(0.3) def drain(self): with self.lock: @@ -307,6 +335,7 @@ def main(): last_pid = pid seen = {} seen_sems = set() + clear_trace() if sock is not None: try: sock.sendall(("#pid %d\n" % pid).encode()) |