This removes all the code for add-on performance watching from the
perfmonitoring component. This should mean that for add-on
compartments, we no longer trigger jank or CPOW monitoring in the JS
engine. This should result in minor performance improvements. As a
result, about:performance no longer reports on add-on performance
(but still reports on web page performance).
It also removes the AddonWatchers.jsm module and the related Nightly-
only UI (disabled in the parent commit) and strings. This UI wasn't
ready for release, there wasn't sufficient data it was creating
value for users, and there was some evidence that it didn't always
correctly identify the cause of performance issues, thus potentially
leading to user confusion or annoyance. Removing it therefore seemed
the right thing to do.
MozReview-Commit-ID: LsRwuaUtq6L
This patch fixes two related issues.
1. The AutoStopwatch uses a stack-allocated `mozilla::Vector` to
communicate with its callback during each compartment switch. This
vector was designed to allow its contents to be stack-allocated but
they turned out to be accidentally heap-allocated.
2. During each tick, the stopwatch fills a vector
`recentGroups_`. This vector always started with minimal capacity and
had to grow repeatedly as groups were added, causing repeated
reallocations. This patch preallocates `recentGroups_` to have the
same capacity as the previous tick. We expect that this should
eventually reach a stable size that closely matches the actual needs
of the process.
MozReview-Commit-ID: A7e3HNdSuML
Although I haven't been able to pinpoint why, it looks like
nsPerformanceStatsService::Dispose() may be called twice, which in
turn causes crashes. This patch makes sure that calling the method
twice is idempotent.
Also, just in case this was due to a typo in
AddObserver/RemoveObserver, this patch replaces the literal strings
used in both with constants.
MozReview-Commit-ID: 8fXO20r5xvO
Although I haven't been able to pinpoint why, it looks like
nsPerformanceStatsService::Dispose() may be called twice, which in
turn causes crashes. This patch makes sure that calling the method
twice is idempotent.
Also, just in case this was due to a typo in
AddObserver/RemoveObserver, this patch replaces the literal strings
used in both with constants.
MozReview-Commit-ID: 8fXO20r5xvO
This patch (currently WIP) alters the way we determine whether jank is user-visible or not.
Instead of measuring the total time spent doing JS, we now use an
indicator provided by the vsync driver: how long it takes to deliver
the signal from the vsync timer to the main thread. This lets us find
out more accurately if there is user-visible jank. In the future, this
will also let us add an observer to find out whether the process
itself is janky, regardless of JS.
To decrease the number of apparent false positives, we classify jank
alerts as visible or invisible. We use the following heuristic:
- if the process is currently animating something, any jank alert is visible;
- if the process has just handled a user input, any jank alert is visible;
- if some user input is handled during the current iteration, any jank alert is visible;
- otherwise, jank alerts are not visible.
This patch introduces a new API to the nsPerformanceStatsService to register observers for slow performance. This API has several advantages:
- as it doesn't require polling, it also doesn't need to wake up the parent process every 15 seconds for the AddonWatcher;
- as it doesn't require polling, it doesn't need to wake up the child processes every time we wish to obtain data on slow performance;
- as it provides immediate data on performance alerts, it makes it possible to get rid of the complex and expensive post-processing performed by JS to merge data from all processes and attempt to extract performance alerts.
The old API is still available.
