2. App State 64K object pools
Large (>16K) and
Fast free
huge objects (>64K)
Pool 2 Per app domain
finalizer thread
Pool 0 Pool 1
3. Targeted towards diverse devices
Non generational mark-sweep-compaction
Highest cost is compaction
◦ Fired when fragmentation > 750K
GC can trigger code pitching
GC triggers
◦ Allocation fails
◦ Quanta of allocation
◦ User code forces GC
◦ When app goes to background
4. Actively engaging with
◦ Desktop SL team
◦ Desktop CLR GC folks
◦ XNA team
Measure, measure and then measure some
more
Development of tools for memory simulations
5. 60% to 85% of memory in native heap with 80
MB working set
◦ Native heap allocations don’t impact GC perf
◦ Images, in native heap, dominate working set
Desktop GC inadequate in this scenario
Unsuccessfully attempted Add/Remove
Memory pressure
SL drives GC
Suggested we tweak our GC to be total
memory aware and expose hosting API
6.
7.
8. Samsung Mirage
250
200
150
GC latency
Garbage per sec:100K
(milli sec)
100
50
0
1 2 3.2 4.3 5.5 6.7 7.8 9 10
Managed Heap Working Set
OMAP - 10 mb managed data
1. Without 60ms
2. With compaction 186ms
3. 26MB Compaction 324ms
9. 60-80% of working set is native
Linear degradation with increase in managed
working set
Expected max is 50MB
Managed WS < 10MB generally works fine
Managed WS >100MB experiences “hangs”
UI over web-services, small data works fine
UI over large in-memory data has large startup
time
Multi-media, games can have small freezes
(200ms) on full GC
SL apps with lot of native memory may run into
OOM even when memory can be reclaimed
10. Refactoring to allow GC in-built profiles
Auto-tuning to reduce the number of GC
Configurability
Hosting changes
11. Auto tune internal thresholds
◦ Collection threshold/budget
◦ Fragmentation threshold for compaction
Native allocation aware
System memory aware
Low memory state
12. Support GC policies
◦ Currently limited hand tuning for entire CLR
◦ Per process GC config (*.exe.config)
Downloaded application cannot override
System applications can change Quanta, disable
pitching
Add GC Hosting API’s
◦ ICLRHostManager::Collect
◦ ICLRManager::SetGCStartupLimits
◦ IHostMemoryManager::GetMemoryLoad
◦ IHostGCManager::GCNotification
13. CE 6.0 memory model changes
Hand optimization
Generational GC
◦ Current data on desktop SL suggests against it
14. Xbox and other large systems bring in special
challenges
Per CPU heap/allocation context
Parallel GC on multi-proc systems
Pre-fetch
Current focus is Mobile scenarios
Take AwayBasic understanding of how NETCF GC Works
Allocation from the end (no searching for holes)
Works on WinMo, CE devices, Xbox, Zune. But primarily targeted towards low-mem deviceUses grow able mark buffers with failoverCompacts when fragmentation reaches 750KCompaction based on Jonker’s (chaining) algorithmGC triggersNon-adaptive with registry tweaks
