Project Fission/Memory
Goals
Due to the drastic increase in the number of processes required to support Project Fission we must focus on reducing the per-process overhead of each content process. As a baseline, we are working on reducing the amount of memory used to load an about:blank page.
Metrics
Binary Section Sizes
Any writable data will increase the overhead of each content process, this is particularly problematic on Linux and OSX. This data is tracked via section_size entries in build_metrics in perfherder.
Are We Slim Yet Tests
The primary tests used by MemShrink are the Are We Slim Yet (AWSY) suite. Metrics are available in perfherder under the awsy framework.
AWSY (sb)
Our main focus for Fission is the simpler about:blank SY-e10s(ab) test. This gives a less noisy baseline metric that allows us to focus on incremental improvements. This is essentially our best case metric.
Metrics
Resident Unique is our main measurement of success. It's the total amount of memory that the content process is using that's not shared with other processes:
JavaScript is memory used by our JavaScript engine both for it's internal state and any loaded scripts. It is one of the largest contributors to memory overhead, has very little noise, and has been a focus for memory reduction:
- JavaScript Memory - Linux
- JavaScript Memory - Windows
- JavaScript Memory - OSX
- JavaScript Memory - Regression view
This is useful for tracking down where a regression started by breaking out integration branches. It's limited to just Linux, but JS is generally platform agnostic.
Testing your changes
To run locally use:
./mach awsy-test testing/awsy/awsy/test_base_memory_usage.py
To run on try for comparisons use:
hg up base_revision ./mach try -b o -p linux64 -u awsy-base-e10s -t none --rebuild 5 hg up new_revision ./mach try -b o -p linux64 -u awsy-base-e10s -t none --rebuild 5
AWSY (sy)
The original test suite, SY-e10s(sy), is a stress test that loads 100 pages into 30 tabs 3 times and measures memory at various points and is useful for detecting regressions in startup memory usage, longer term leaks, leaked windows, etc. This is essentially our worst case metric.
Metrics
after tabs opened is one of several data points gathered, it is the most relevant to this project:
- Resident Memory - Linux [regression view]
- Resident Memory - Windows [regression view]
- Resident Memory - OSX [regression view]
Testing your changes
To run locally use:
./mach awsy-test
To run on try for comparisons use:
hg up base_revision ./mach try -b o -p linux64 -u awsy-e10s -t none --rebuild 5 hg up new_revision ./mach try -b o -p linux64 -u awsy-e10s -t none --rebuild 5
AWSY (tp6)
An updated test suite, SY-e10s(tp6), is a test that loads the entire tp6 pageset and measures memory at various points. The tp6 pageset uses mitmproxy to simulate live connections which will allow us to properly test out-of-process iframes.
Metrics
Currently we're not tracking these metrics, they'll be more interesting once we enable fission.
Testing your changes
To run locally use:
./mach awsy-test --tp6 --preferences testing/awsy/conf/tp6-prefs.json
To run on try for comparisons use:
hg up base_revision ./mach try fuzzy --rebuild 5 -q "'linux64/opt-awsy-tp6" hg up new_revision ./mach try fuzzy --rebuild 5 -q "'linux64/opt-awsy-tp6"
Meetings
Meetings happen every other Tuesday at 12:00pm Pacific time (countdown in your timezone)
- Dial-in: Audio-only conference# 8394
- People with Mozilla phones or softphones please dial x4000 Conf# 8394
- US/Toll-free: +1 800 707 2533, (pin 4000) Conf# 8394
- US/California/Mountain View: +1 650 903 0800, x4000 Conf# 8394
- US/California/San Francisco: +1 415 762 5700, x4000 Conf# 8394
- US/Oregon/Portland: +1 971 544 8000, x4000 Conf# 8394
- CA/British Columbia/Vancouver: +1 778 785 1540, x4000 Conf# 8394
- CA/Ontario/Toronto: +1 416 848 3114, x4000 Conf# 8394
- UK/London: +44 (0)207 855 3000, x4000 Conf# 8394
- FR/Paris: +33 1 84 88 37 37, x4000 Conf# 8394
- Gmail Chat (requires Flash and the Google Talk plugin): paste +1 650 903 0800 into the Gmail Chat box that doesn't look like it accepts phone numbers
- SkypeOut is free if you use the 800 number
- Vidyo: MemShrink
- IRC: #memshrink
Bug Tracking
Tracking: bug 1436250
Triage
We use the [overhead] whiteboard tag to flag items for triage. Additionally any bug in the bug 1436250 dependency tree is generally triaged. The triage process attempts to estimate the impact a bug will have on reducing the overhead of a content process. If we think a bug will reduce per-process memory usage by 30KB then update the tag with the expected win: [overhead:30K]. We try to use a reasonable guess for this value, it doesn't need to be exact.
Progress
Measurements from the beginning of each quarter.
Linux
| Quarter | Resident Unique | JS |
|---|---|---|
| Q2 2018 | 34.3MB | 8.5MB |
| Q3 2018 | 33.6MB | 8.0MB |
| Q4 2018 | 20.7MB | 5.3MB |
| Q4.5 2018 | 17.8MB | 4.6MB |
| Q1 2019* | 19.5MB | 5.0MB |
| Q2 2019 | 19.5MB | 4.1MB |
| Q3 2019 | 19.5MB | 4.1MB |
Windows
| Quarter | Resident Unique | JS | Resident Unique (WebRender) |
|---|---|---|---|
| Q2 2018 | 21.5MB | 8.5MB | N/A |
| Q3 2018 | 20.8MB | 8.0MB | N/A |
| Q4 2018 | 15.0MB | 5.3MB | 17.1MB |
| Q4.5 2018 | 15.0MB | 4.8MB | 17.1MB |
| Q1 2019* | 17.8MB | 5.1MB | 14.5MB |
| Q2 2019 | 15.1MB | 4.1MB | 14.8MB |
| Q3 2019 | 15.1MB | 4.1MB | 14.8MB |
OSX
| Quarter | Resident Unique | JS |
|---|---|---|
| Q2 2018 | 32.7MB | 8.5MB |
| Q3 2018 | 31.7MB | 8.0MB |
| Q4 2018 | 21.4MB | 5.3MB |
| Q4.5 2018 | 20.4MB | 4.6MB |
| Q1 2019* | 25.2MB | 5.0MB |
| Q2 2019 | 24.6MB | 4.1MB |
| Q3 2019 | 24.6MB | 4.1MB |
- Q1 2019 note: We switched to VMs with GPUs to better simulate real-world conditions. This resulted in apparent regressions across the board.