Javascript:SpiderMonkey:ProjectGenerationGarbageCollection
From MozillaWiki
|
THIS PAGE MAY BE OUTDATED |
| This article is in parts, or in its entirety, outdated. Hence, the information presented on this page may be incorrect, and should be treated with due caution until this flag has been lifted. Help by editing the article, or discuss its contents on the talk page. |
Wiki conversion of original Google Document: https://docs.google.com/a/jamsni.com/document/d/1-GZ8F0ZabvdpCnRQaecId0yuu4QFYr5pAvnRC_KFchc/edit
Contents
- 1 Objective
- 2 Milestones
- 3 Steps
- 3.1 Exact Rooting done in JS Shell bug 753203
- 3.2 JIT Integration with post barriers - 4 weeks, parallelized
- 3.3 Generational Garbage Collection in the Shell
- 3.4 Exactly Root the Browser bug 831379 - 10 weeks
- 3.5 Performance Tuning - 4 weeks (This should probably start asap)
- 3.6 Make the Post Barrier Verifier Green in the browser bug 764882
- 4 Other
- 5 Risks
Objective
Implement Generational Garbage collection in Spider Monkey. <Some goal based off V8 performance delta % on Earley Boyer benchmark>
Accountable: Naveed
Responsible: Terrence, Steve, Jon, Nicholas, evilpie and Ms2ger
Consulted: bhackett billm
Informed: Product Marketing
Tracking Bug: [meta] Implement generational garbage collection - bug 619558
Milestones
Endgame schedule
- Burndown of rooting hazards and unsafe references: https://people.mozilla.com/~sfink/analysis
- Burndown of bugs blocking Exact Rooting: https://metrics.mozilla.com/...
| Milestone | Bug | Old Estimated Date | Current Estimated Date | Actual Date | Nightly Version |
|---|---|---|---|---|---|
| ... | |||||
| Nightly 26 (B2G 1.2) is uplifted to Aurora | 2013-09-16 | ||||
| All unsafe references found by static analysis have been fixed | 898608 | 2013-09-23 | 2013-10-02 | 27 | |
| Static analysis of unsafe references is unhidden on TBPL | 834909 | 2013-09-25 | 2013-10-03 | 27 | |
| All rooting hazards found by static analysis have been fixed | 898606 | 2013-10-18 | 2013-10-07 | 27 | |
| Static analysis of rooting hazards is unhidden on TBPL | 834909 | 2013-10-22 | 2013-10-08 | 27 | |
| Nightly 27 is uplifted to Aurora | 2013-10-28 | ||||
| ... | 28 | ||||
| All GGC crashes found by fuzzers have been fixed | 877471 | 2013-11-__ | 2013-10-__ | 28 | |
| AWFY with GGC >= AWFY without GGC | 875863 | 2013-11-__ | 28 | ||
| GGC is enabled for desktop and Android | 619558 | 2013-11-__ | 28 | ||
| GGC is enabled for B2G 1.3 | 619558 | 2013-11-__ | 28 | ||
| ... | 28 | ||||
| Nightly 28 (B2G 1.3) is uplifted to Aurora | 2013-12-09 | ||||
| ... | 29 | ||||
| Nightly 29 is uplifted to Aurora | 2014-01-20 | ||||
| ... | 30 |
Original schedule
| Milestone | Task | Deliverable | Assigned | Estimated Weeks | Expected Date | Actual Date |
|---|---|---|---|---|---|---|
| 1 | Rooting analysis in the shell (x64) | green on mozilla-inbound | sfink, jonco, evilpie, Ms2ger | 2 | 3/7/2013 | 3/2/2013 |
| 2 | Rooting analysis in the shell (arm) | green on mozilla-inbound | sfink | 2 | pending | |
| 3 | Exactly rooted shell (x64) | green on mozilla-inbound | sfink, jonco, evilpie, Ms2ger | 2 | 3/14/2013 | done? |
| 4 | Exactly rooted shell (arm) | green on mozilla-inbound | sfink | 2 | pending | |
| 4.1 | Exactly rooted js/src | green on mozilla-inbound | jonco | 3 | 5/9/2013 | in progress |
| 5 | GGC no-jit shell only build on TBPL (x64) | green on mozilla-inbound | terrence | 6 | 2/21/2013 | 4/7/2013 |
| 6 | GGC no-jit shell only build on TBPL (arm) | green on mozilla-inbound | sfink, terrence | 2 | pending | |
| 7 | JIT support (x64) (Bug 706885) | TBPL build using JITs and Ion+Baseline+GGC displayed on AWFY | bhacket | 8 | 3/15/2013 | 4/7/2013 |
| 8 | JIT support (arm) | TBPL build using JITs and Ion+Baseline+GGC displayed on AWFY | bhacket | 2 | pending | |
| 9 | Optimized GGC in shell (x64 + arm) | Ion+GGC faster than Ion-GGC on AWFY | bhacket | 12 | 6/1/2013 | not started |
| 10 | Static rooting analysis - browser | available via mrgiggles and URL | sfink, bhacket | 12 | 6/1/2013 | done |
| 10.1 | Static analysis on TBPL - browser | visible on tbpl | sfink | not started | ||
| 10.2 | Static rooting analysis - b2g | available via mrgiggles and URL | sfink | pending | ||
| 10.3 | Static analysis on TBPL - b2g | visible on tbpl | sfink | not started | ||
| 11 | Exactly rooted browser (x64 + arm) | green on mozilla-inbound | sfink, jonco, evilpie, Ms2ger, terrence | 16 | 7/1/2013 | in progress |
| 12 | GGC in the browser (x64 + arm) | green on AWFY | terrence | 16 | 10/1/2013 | not started |
Steps
Exact Rooting done in JS Shell bug 753203
12 weeks started
- Dynamic rooting analysis on tbpl (sfink) - done
- Unhidden on inbound
- Get the root analysis build green - done
- Get jit-tests green bug 745742
- Get js ref tests green
- Get jsapi-tests green bug 831376
- Rooting analysis fuzz bugs bug 773746
- Rely on static analysis to make this not be a whack-a-mole game
- Remove E4X - done
- Do something about JSD
- Add exact roots to stack structures - 2 weeks
- AddRoot/RemoveRoot for Heap structures - 4 weeks
- Static code analysis bug 831409
- Fix all discovered rooting hazards (~800) (sfink,jonco) - 4 weeks
- Optimize all discovered over-rooting (~100)
- Automate static analysis bug 834912 - done (sfink)
- http://people.mozilla.org/~sfink/analysis/browser/rootingHazards.txt
- http://people.mozilla.org/~sfink/analysis/browser/gcFunctions.txt
- http://people.mozilla.org/~sfink/analysis/browser/allFunctions.txt
JIT Integration with post barriers - 4 weeks, parallelized
- IonMonkey bug 831506 - 1 week (bhackett)
- JaegerMonkey bug 764876 - 2 days (bhackett)
- Baseline JIT bug 831507 - <ask jandem/djvj for an estimate>
Generational Garbage Collection in the Shell
- Implement prototype algorithm (terrence) - 1 week
- This is a potential milestone: we would need to build it and test it on TBPL similar to how |r| works now -- |GGCJS| - done.
- Re-implement HashTable rekeying
- We undid this code because it was a perf regression and was still a bit buggy. (terrence) - 3 weeks
- at least part of this is bug 726687
Exactly Root the Browser bug 831379 - 10 weeks
- This is a potential milestone: we would turn on exact rooting for release FF at this point. We would not get a performance boost from this (necessarily), but it would lock in our work to this point.
Performance Tuning - 4 weeks (This should probably start asap)
- Implement a Nursery bug 706885 - 1 week
- Test against V8 Earley-Boyer benchmark.
- Also v8 deltablue, raytrace
- We may need to Implement Bill’s Pools/Zones idea to get the nursery to the requisite perf bug 759585 - 6 weeks - done
- Refactor code to avoid rooting on hot paths and keep rooter overhead acceptable bug 831886 (bhackett) - done
Make the Post Barrier Verifier Green in the browser bug 764882
- Investigate how long it will take to do generational barriers - 1 week
- We may need to rewrite the maps in xpconnect and the browser in terms of HashTable: this could be a bunch of work.
- Make JS_IsAboutToBeFinalized indirect bug 765432 - 10 weeks
Other
- Should we establish a new benchmark specifically for GGC. (sfink votes yes)
- What would it measure? there are multiple goals, e.g. throughput/MMU/pause time
- Should we make it a public benchmark?
- What workloads should we consider?
- compartmental GC very important to us, not necessarily applicable to other implementations
- allocation rate (broken down into live vs garbage), steady behavior vs swapping between allocation + computation modes, etc.
- How can we keep our advantage on Splay benchmark
- possible to do with TI --- look at types of objects promoted from nursery to major heap, eventually start allocating them directly in the major heap
- Compacting GC - Revisit in Febuary/March - 1 Month
- Delayed until exact rooting is fully done. We can add this in if we have time in the schedule that we cannot parallelize.
Risks
- Team is responsible for many top crashers
- External rooting API has not been designed
- GGC algorithm has not been decided on - it may not be faster
- JSD1 exact rooting is lurking
