This implements coalescing of progress events using a timeout, as
discussed in the RFC on Discourse [1]. This PR consists of two commits
which, depending on the feedback, I may split up into two PRs. For now,
I think it's easier to review this as a whole.
1. The first commit introduces a new generic `Alarm` class. The class
lets you to schedule a function (callback) to be executed after a given
timeout expires. You can cancel and reset a callback before its
corresponding timeout expires. It achieves this with the help of a
worker thread that sleeps until the next timeout expires. The only
guarantee it provides is that your function is called no sooner than the
requested timeout. Because the callback is called directly from the
worker thread, a long running callback could potentially block the
worker thread. I intentionally kept the implementation as simple as
possible while addressing the needs for the `ProgressManager` use case.
If we want to rely on this somewhere else, we can reassess whether we
need to address those limitations.
2. The second commit uses the Alarm class to coalesce progress events.
To recap the Discourse discussion, when multiple progress events with
the same title execute in close succession, they get broadcast as one to
`eBroadcastBitProgressCategory`. The `ProgressManager` keeps track of
the in-flight progress events and when the refcount hits zero, the Alarm
class is used to schedule broadcasting the event. If a new progress
event comes in before the alarm fires, the alarm is reset (and the
process repeats when the new progress event ends). If no new event comes
in before the timeout expires, the progress event is broadcast.
[1]
https://discourse.llvm.org/t/rfc-improve-lldb-progress-reporting/75717/
This implements coalescing of progress events using a timeout, as
discussed in the RFC on Discourse [1]. This PR consists of two commits
which, depending on the feedback, I may split up into two PRs. For now,
I think it's easier to review this as a whole.
1. The first commit introduces a new generic `Alarm` class. The class
lets you to schedule a function (callback) to be executed after a given
timeout expires. You can cancel and reset a callback before its
corresponding timeout expires. It achieves this with the help of a
worker thread that sleeps until the next timeout expires. The only
guarantee it provides is that your function is called no sooner than the
requested timeout. Because the callback is called directly from the
worker thread, a long running callback could potentially block the
worker thread. I intentionally kept the implementation as simple as
possible while addressing the needs for the `ProgressManager` use case.
If we want to rely on this somewhere else, we can reassess whether we
need to address those limitations.
2. The second commit uses the Alarm class to coalesce progress events.
To recap the Discourse discussion, when multiple progress events with
the same title execute in close succession, they get broadcast as one to
`eBroadcastBitProgressCategory`. The `ProgressManager` keeps track of
the in-flight progress events and when the refcount hits zero, the Alarm
class is used to schedule broadcasting the event. If a new progress
event comes in before the alarm fires, the alarm is reset (and the
process repeats when the new progress event ends). If no new event comes
in before the timeout expires, the progress event is broadcast.
[1]
https://discourse.llvm.org/t/rfc-improve-lldb-progress-reporting/75717/
- Factor our common setup code.
- Split the ProgressManager test into separate tests as they test
separate things.
- Fix usage of EXPECT (which continues on failure) and ASSERT (which
halts on failure). We must use the latter when calling GetEvent as
otherwise we'll try to dereference a null EventSP.
Currently, progress events reported by the ProgressManager and broadcast
to eBroadcastBitProgressCategory always specify they're complete. The
problem is that the ProgressManager reports kNonDeterministicTotal for
both the total and the completed number of (sub)events. Because the
values are the same, the event reports itself as complete.
This patch fixes the issue by reporting 0 as the completed value for the
start event and kNonDeterministicTotal for the end event.
This commit adds the functionality to broadcast events using the
`Debugger::eBroadcastProgressCategory`
bit (https://github.com/llvm/llvm-project/pull/81169) by keeping track
of these reports with the `ProgressManager`
class (https://github.com/llvm/llvm-project/pull/81319). The new bit is
used in such a way that it will only broadcast the initial and final
progress reports for specific progress categories that are managed by
the progress manager.
This commit also adds a new test to the progress report unit test that
checks that only the initial/final reports are broadcasted when using
the new bit.
This file was previously approved and merged from this PR:
https://github.com/llvm/llvm-project/pull/79533 but caused a test
failure on the Linux AArch64 bots due to hitting an assertion that
`Debugger::Initialize` was already called.
To fix this, this commit uses the
changes made here: https://github.com/llvm/llvm-project/pull/80786 to
use a shared call_once flag to initialize the debugger.
This reverts commit a5a8cbb110384825b99228891576f799082f200e.
The test being added by that commit still fails on the assertion that
Debugger::Initialize has been called more than once.
This reverts commit 209fe1f3d70d1c4a20bb2687e0d0a94b1bbfa0c6.
The original commit failed to due an assertion failure in the unit test
`ProgressReportTest` that the commit added. The Debugger::Initialize()
function was called more than once which triggered the assertion, so
this commit calls that function under a `std::call_once`.
This reverts commit 51e0d1b707a15dd3b96e0c4f1a29ca4dfc79cda0.
That commit breaks a unit test:
```
Failed Tests (1):
lldb-unit :: Core/./LLDBCoreTests/4/8
```
This test is being added as a way to check the behaviour of how progress
events are broadcasted when reports are started and ended with the
current implementation of progress reports. Here we're mainly checking
and ensuring that the current behaviour is that progress events are
broadcasted individually and placed in the event queue in order of their
creation and deletion.
