Performance/MemShrink
MemShrink is a project that aims to reduce Firefox's memory consumption. There are three potential benefits.
- Speed. Firefox will be faster due to less cache pressure, less paging, and fewer/smaller GC and CC pauses. Changes that reduce memory consumption but make Firefox slower are not desirable.
- Stability. Firefox will suffer fewer aborts/crashes due to virtual or physical memory exhaustion. The former is mostly a problem on 32-bit Windows builds with a 2GB or 4GB virtual memory limit, the latter is mostly a problem on mobile devices that lack swap space.
- Reputation. Fewer people will complain that Firefox is a memory hog and that Mozilla ignores memory usage.
This blog post describes these benefits in more detail.
There are two main ways to reduce memory consumption.
- "Slim down" memory usage, e.g. make data structures more space-efficient.
- Avoid "leaks". This loose use of the term (which is used throughout this document) includes:
- True leaks, where memory is lost forever.
- Lifetime issues, where memory is not reclaimed until you close the page/tab/window/process.
- Collection heuristic issues (e.g. GC is too infrequent).
- Bad cache algorithms and poorly tuned caches.
- Fragmentation.
Leaks are generally more important, because they are more likely to lead to horrible performance.
Meetings
Meetings happen every second Tuesday at 2pm Pacific time.
- Dial-in: Audio-only conference# 95346
- People with Mozilla phones or softphones please dial x4000 Conf# 95346
- US/Toll-free: +1 800 707 2533, (pin 4000) Conf# 95346
- US/California/Mountain View: +1 650 903 0800, x4000 Conf# 95346
- US/California/San Francisco: +1 415 762 5700, x4000 Conf# 95346
- US/Oregon/Portland: +1 971 544 8000, x4000 Conf# 95346
- CA/British Columbia/Vancouver: +1 778 785 1540, x4000 Conf# 95346
- CA/Ontario/Toronto: +1 416 848 3114, x4000 Conf# 95346
- UK/London: +44 (0)207 855 3000, x4000 Conf# 95346
- FR/Paris: +33 1 84 88 37 37, x4000 Conf# 95346
- 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: PB&J
- IRC: #memshrink
- Etherpad: memshrink (copied to wiki after the meeting)
Meeting Minutes, Progress Reports and Presentations
Meeting dates, meeting minutes, and progress reports.
| Date | Minutes | Progress report |
|---|---|---|
| 2013-02-05 | - | Week 85--86 |
| 2013-01-22 | - | Week 83--84 |
| 2013-01-08 | - | Week 79--82 |
| 2012-12-11 | - | Week 77--78 |
| 2012-11-27 | - | Week 75--76 |
| 2012-11-13 | - | Week 73--74 |
| 2012-10-30 | - | Week 71--72 |
| 2012-10-16 | - | Week 69--70 |
| 2012-10-02 | - | Week 67--68 |
| 2012-09-18 | - | Week 65--66 |
| 2012-09-04 | - | Week 63--64 |
| 2012-08-21 | - | Week 61--62 |
| 2012-08-07 | - | Week 57--60 |
| 2012-07-24 | - | - |
| 2012-07-10 | - | Week 55--56 (includes the second "Big Ticket Items" list) |
| 2012-06-26 | - | Week 53--54 |
| 2012-06-14 | - | MemShrink's 1st Birthday |
| 2012-06-12 | - | Week 51--52 |
| 2012-05-29 | - | Week 49--50 |
| 2012-05-15 | - | Week 47--48 |
| 2012-05-01 | - | Week 45--46 |
| 2012-04-17 | - | Week 43--44 |
| 2012-04-03 | - | Week 42 |
| 2012-03-27 | - | Week 41 |
| 2012-03-20 | - | Week 40 |
| 2012-03-13 | - | Week 39 |
| 2012-03-06 | - | Week 38 |
| 2012-02-28 | - | Week 37 |
| 2012-02-21 | - | Week 36 |
| 2012-02-14 | - | Week 35 |
| 2012-02-07 | - | Week 34 |
| 2012-01-31 | - | Week 33 |
| 2012-01-24 | - | Week 32 (includes the first "Big Ticket Items" list) |
| 2012-01-17 | - | Week 31 |
| 2012-01-10 | - | Week 30 |
| 2012-01-03 | - | Weeks 28--29 |
| 2011-12-20 | - | Week 27 |
| 2011-12-13 | minutes | Week 26 |
| 2011-12-06 | minutes | Week 25 |
| 2011-11-29 | minutes | Week 24 |
| 2011-11-22 | - | Week 23 |
| 2011-11-15 | - | Week 22 |
| 2011-11-08 | minutes | Week 21 |
| 2011-11-01 | minutes | Week 20 |
| 2011-10-25 | minutes | Week 19 |
| 2011-10-18 | minutes | Weeks 13--18 |
| 2011-10-11 | minutes | - |
| 2011-10-04 | minutes | - |
| 2011-09-27 | - | - |
| 2011-09-20 | minutes | - |
| 2011-09-13 | - | - |
| 2011-09-06 | minutes | Week 12 |
| 2011-08-30 | minutes | Week 11 |
| 2011-08-23 | minutes | Week 10 |
| 2011-08-16 | minutes | Week 9 |
| 2011-08-09 | minutes | Week 8 |
| 2011-08-02 | - | Week 7 |
| 2011-07-26 | minutes | Week 6 |
| 2011-07-19 | minutes | Week 5 |
| 2011-07-12 | minutes | Week 4 |
| 2011-07-05 | minutes | Week 3 |
| 2011-06-28 | - | Week 2 |
| 2011-06-21 | - | Week 1 |
| 2011-06-14 | - | - |
Presentations.
- 2012-01-16 "Notes on Reducing Firefox's Memory Consumption", presented at linux.conf.au Browser MiniConf
Bug Tracking
Bugs tracked by the MemShrink project are prioritized by adding one of "MemShrink:P1", "MemShrink:P2" or "MemShrink:P3" to the whiteboard.
- Unprioritized MemShrink bugs. These are triaged regularly in meetings.
- MemShrink:P1 bugs. These are discussed regularly in meetings.
- MemShrink:P2 bugs. These are discussed occasionally in meetings. P2 is the default priority.
- MemShrink:P3 bugs. These are discussed rarely in meetings.
Some other interesting bug lists that overlap with the ones above.
- All MemShrink bugs.
- Unconfirmed MemShrink bugs. These are problems reported by users and generally require some kind of additional work to confirm.
- MemShrink bugs with a "mentor" annotation. These are bugs that someone has identified as reasonable easy, and that person is willing to help a newcomer fix the bug.
- Unassigned MemShrink bugs. These need someone to work on them.
areweslimyet.com
http://arewefastyet.com is a very successful site used to track the performance of Firefox's JavaScript engine. Why was arewefastyet.com so successful? Some key characteristics.
- The benchmarks were easy to choose: everybody already used SS and V8, and then Mozilla released Kraken. They run quickly, too, which is nice for devs, and allows expensive tools (like Cachegrind) to be used.
- The metrics were easy to choose. SS time, V8 time, Kraken time. They can be measured easily, precisely, and fairly repeatably. You can break the total time down into per-benchmark times, which really helps with understanding improvements and regressions. They're easy for devs to run on their own machine.
- There was a well-defined goal: match or beat the other browsers.
In comparison, for memory consumption there is no good and/or standard benchmark suite; metrics are less clear and harder to measure (especially across different browsers); and most importantly, there's no well-defined goal w.r.t. any benchmarks.
Nonetheless, we've created a memory benchmark and are tracking Firefox's performance on it over time, to provide a sense of MemShrink progress and detect regressions. It is available at http://areweslimyet.com/.