Implement ftrace flushing
This CL finally implements flushing of ftrace data and
wires it up to the Flush() API of the tracing service.
The major change introduced is in CpuReader, the multi
threaded class that reads ftrace data.
The core scheduling algorithm is left unchanged (see
//docs/ftrace.md). The old logic is still preserved:
[wait for command] -> [splice blocking] -> [splice nonblock]
However, this CL introduces a way for the FtraceController
to interrupt the splice and switch to read() mode for
flushes. read(), in fact, is the only way to read partial
pages out of the ftrace buffer.
Even when in read() mode, the scheduling algorithm is still
the same, just s/splice/read/.
There are a bunch of caveats and they are thoroughly
described in b/120188810. Essentially once we switch to
read() for the flush, we need to be careful and wait for
the ftrace read pointer to become page-aligned again before
switching back to splice().
Furthermore this CL gets rid of the internal pipe to move
data between the worker thread and the main thread and switches
to the recently introduced page pool. We still have an internal
pipe (for splice) but use it entirely in the worker therad.
Exposing the pipe to the main thread had two drawbacks:
1) Essentially limits the transfer bandwidth between the worker
thread and the main thread, making the ftrace buffer size
useless. Before, even if one specified a buffer size of 1GB,
we would at most read 1 pipe buffer per read cycle.
2) That hits another kernel bug around non-blocking splice
(b/119805587).
Test: perfetto_integrationtests --gtest_filter=PerfettoTest.VeryLargePackets
Bug: 73886018
Change-Id: I4a6e82b284971a3765b42959904f5402095e4c4e
diff --git a/test/test_helper.h b/test/test_helper.h
index 2bd4cf0..599ce5d 100644
--- a/test/test_helper.h
+++ b/test/test_helper.h
@@ -43,11 +43,13 @@
FakeProducer* ConnectFakeProducer();
void ConnectConsumer();
void StartTracing(const TraceConfig& config);
+ void DisableTracing();
+ void FlushAndWait(uint32_t timeout_ms);
void ReadData(uint32_t read_count = 0);
void WaitForConsumerConnect();
void WaitForProducerEnabled();
- void WaitForTracingDisabled();
+ void WaitForTracingDisabled(uint32_t timeout_ms = 5000);
void WaitForReadData(uint32_t read_count = 0);
std::function<void()> WrapTask(const std::function<void()>& function);