"History, Goals, Objectives, and Structure of DragonFlyBSD"
2:02 PM What is DragonFlyBSD?
* FreeBSD started from FreeBSD and maintains binary compatibility
* Designed for modern systems. In particular, SMP isn't a valid multi-processing model anymore; multiple processor
systems aren't symetric.
2:10 good things about FreeBSD
* Robust VM
* Ports collection
* softupdates
* TCP/IP stack
2:12 Good things about Linux
* RCU
* 1:1 threads
* Device drivers
2:14 Good things about NetBSD
* altq
* pkgsrc—-os indepenance
2:16 Good things about OpenBSD
* pf
* propolice
* W^R
2:17 New in DragonFlyBSD
* ACPI
* messaging infrastucture
* simpultaneous threading across processors (1:1 threads)
* parallel TCP stack, parallel routing table. Split TCP/IP stack across multiple processors
* TCP SACK return list of unreceived packets (15% improvement in throughput)
* TCP ABC protection against ACK attacks
* altq
* SCTP
* name cache—negative name caching—big win for NFS
* MMX optimized bzero
* variant symlinks (e.g. 'ln -s '${os}bin' /pbin')
* process checkpointing—save state and restart processes
2:27 Organization
* Intended to be lean for quick development and easy consensus
2:28 Goals
* Fast
* Stable
* Support contemporary hardware
2:29 New Concepts
* Messaging as a kenerl structure for parallelism
* Lightweight kernel threads. low overhead for accounting
* Tokens—mutex replacement
2:34 Networking advancements
* TCP never recovers from a slow start because you're locked into a 4 RT cycle once you miss an ACK
* larger window sizes let you send more packets and reduce retransmit cycle times
* Limited transmit
* Eifel detection
* Early retransmit
