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Performance Bottlenecks (Timers (Actions (StartTimer, StopTimer,…
Performance Bottlenecks
Copying
Caused by
Protection
Structure
TCP
4 Copies
1: Disk -> FileCache
2: File Cache -> Server Buffer
3: ServerBuffer -> Socket Buffer
4: Socket Buffer -> Network Adaptor
Avoid by
Exploiting Adaptor Memory
Witless Aproach
Afterburner Adaptor
Copy-On-Write
Direct OS Support
Virtual Memory
Fbufs (Cache page mapping info)
DMA
Context Switching
Caused by
Complex Sheduling
Avoid by
Upcalls
System Calls
Caused by
Protection
Structure
Timers
Caused by
Scaling with number of timers
Needed for
System watchdogs
Timeouts
Sheduling algorithms
Actions
StartTimer
StopTimer
PerTickBookkeeping
ExpliryProcessing
Optimizations
Timer Wheels
Sorted List
Hashed Timer Wheels
Demultiplexing
Caused by
Scaling with number of endpoints
Early-Demulitiplexing
Avantages
Prioritizing Packets (QoS)
Specializing paths
Fast dispatching (avoids control overhead)
Checksums/CRCs
Caused by
Generality
Scaling with link speeds
Protocol Code
Caused by
Generality
Exact Lookups
Caused by
Link speed sclaing
Prefix Lookups
Caused by
Link speed scaling
Prefix database size scaling
Security
Caused by
Scaling in number and intensity of attacks
Measurement
Caused by
Link speed scaling
Internal Bandwidth
Caused by
Scaling of internal bus speeds
Fair Queueing
Caused by
Service differentiation
Link speed scaling
Memory scaling
Switching
Caused by
Optical-electronic speed gab
Head-of-line blocking
Packet Classification
Caused by
Service differentiation
Link speed and size scaling