debug: Fix UI freezing on "continue" with high number of threads#283635
debug: Fix UI freezing on "continue" with high number of threads#283635connor4312 merged 3 commits intomicrosoft:mainfrom
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@microsoft-github-policy-service agree company="Meta" |
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| if (needFreshFetchThreads) { | ||
| this.fetchThreadsScheduler.rawValue?.cancel(); | ||
| await this.fetchThreads(); |
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We don't want to await outside the statusQueue since that opens up to race conditions (e.g. DA continues threads and pauses again before this fetchThreads finishes and we end in a torn state)
I think we probably just want to debounce the _onDidChangeCallStack.fire call in DebugModel.clearThreads. You can see how we do that with the fetchThreadsScheduler already today in the debug session, we'd do the same thing there.
Btw reviewing the code I notice a bug in DebugModel.clearThreads -- we don't check the reference (thread ID) when clearing the schedulers. If a thread ID is set, we should only clear its scheduler, not all schedulers. If you're up for fixing a low hanging bug there, feel free to do so 🙂
This fixes a performance regression accidentally introduced in microsoft#265755. Before that change, if the `continued` event had `allThreadsContinued` set, then we'd call `this.model.clearThreads()` passing `undefined` as `threadId`, which would update all threads in one pass. After that change, a call to `this.model.clearThreads()` would be done for each thread. Because each call to `this.model.clearThreads()` ends up calling `this._onDidChangeCallStack.fire()`, we end up with quadratic overhead as some of the handlers traverse all threads in the call-stack box. This would lead to minute long freezes when using the Erlang debugger, to debug a system with ~20K Erlang processes. We now debounce the calls to `_onDidChangeCallStack.fire()` to avoid the issue.
When calling `clearThreads()` on the model, we'd cancel every scheduled action, for every session, instead of those relevant only for the given session and, optionally, thread.
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@connor4312 thanks for the review! I've updated the branch with a new version that instead debounces the calls, and did a drive-by fix of the bug you spotted in |
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| session.clearThreads(removeThreads, reference); | ||
| this._onDidChangeCallStack.fire(undefined); | ||
| this._onDidChangeCallStackFire.schedule(); |
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Small thing: we should schedule only if not already scheduled. Otherwise a DA with a ton of threads and very frequent events could result in the call stack never updating.
| private _onDidChangeCallStackFire = new RunOnceScheduler(() => { | ||
| this._onDidChangeCallStack.fire(undefined); | ||
| }, 100); |
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| private _onDidChangeCallStackFire = new RunOnceScheduler(() => { | |
| this._onDidChangeCallStack.fire(undefined); | |
| }, 100); | |
| private _onDidChangeCallStackFire = this._register(new RunOnceScheduler(() => { | |
| this._onDidChangeCallStack.fire(undefined); | |
| }, 100)); |
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Added a fixup for both issues |
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thanks for the contribution! |
…rosoft#283635) * debug: Fix UI freezing on "continue" with high number of threads This fixes a performance regression accidentally introduced in microsoft#265755. Before that change, if the `continued` event had `allThreadsContinued` set, then we'd call `this.model.clearThreads()` passing `undefined` as `threadId`, which would update all threads in one pass. After that change, a call to `this.model.clearThreads()` would be done for each thread. Because each call to `this.model.clearThreads()` ends up calling `this._onDidChangeCallStack.fire()`, we end up with quadratic overhead as some of the handlers traverse all threads in the call-stack box. This would lead to minute long freezes when using the Erlang debugger, to debug a system with ~20K Erlang processes. We now debounce the calls to `_onDidChangeCallStack.fire()` to avoid the issue. * debug: Avoid cancelling too many scheduled actions when clearing threads When calling `clearThreads()` on the model, we'd cancel every scheduled action, for every session, instead of those relevant only for the given session and, optionally, thread. * fixup! debug: Fix UI freezing on "continue" with high number of threads
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This fixes a performance regression accidentally introduced in #265755.
Before that change, if the
continuedevent hadallThreadsContinuedset, then we'd callthis.model.clearThreads()passingundefinedasthreadId, which would update all threads in one pass. After that change, a call tothis.model.clearThreads()would be done for each thread.Because each call to
this.model.clearThreads()ends up callingthis._onDidChangeCallStack.fire(), we end up with quadratic overhead as some of the handlers traverse all threads in the call-stack box. This would lead to minute long freezes when using the Erlang debugger, to debug a system with ~20K Erlang processes.The solution is to go back to the previous implementation, where
clearThreads()is ever called with one thread-id or withundefined, but first wait onthis.fetchThreads()if needed