The next major release of FreeBSD, version 8, will probably be an "evolutional" release. The focus will be on further improvements of SMP capabilities and the stability of already implemented subsystems. This page will document changes that will be included in FreeBSD 8, including those that might end up being committed to earlier branches. In other words, it describes differences between 7.0 and 8.0, no matter what happens to the versions in between.
Also useful are the quarterly Status Reports:
Everyone's encouraged to download a snapshot CD image and try all the new features (as well as the old ones). Developers are very interested in bug reports. Note that FreeBSD 8.0 is not released yet and both the snapshots and the default source trees have debugging enabled by default (which results in dramatic slowdowns so don't benchmark them without removing the debugging options).
If you're interested in how FreeBSD gets developed, you're encouraged to read the mailing lists and developer blogs.
Kernel & low level improvements
MPSAFETTY
Status: In final stages of development
Will appear in 8.0: probably
Author: Ed Schouten
Web: wiki page
The TTY layer is the traditional Unix interface to system users, providing them with interactive sessions to run shells, etc. The current TTY layer in FreeBSD is for the most part the traditional BSD TTY, which is integrated with the drivers and other layers in a way that, though efficient, makes it hard to maintain and extend. The initiative to rewrite the TTY layer aims to make it a true abstraction layer, operating on behalf of both sides of TTY. In addition, it will remove the TTY from the Giant lock, which will eliminate problems with lags and skippy user interface behaviour in the console and X.Org.
Kernel memory limit on AMD64 increased to 6 GB
Status: Committed to -CURRENT
Will appear in 8.0: sure
Author: Alan Cox
Web: announcement
Some modern features (of which the most notable currently is ZFS) require a large amount of kernel memory (this has nothing to do with traditional disk caches). Up to now, it was only possible to allocate up to 2 GB for kmem_max, which is becoming a bit cramped. There is ongoing work to increase this to at least 6 GB. Users of ZFS will be happy.
Kernel threads
Status: Committed to -CURRENT
Will appear in 8.0: sure
Author: Julian Elischer
Web: commit message
Kernel threads upto now were actually "heavy weight" processes running in the kernel address space. This change introduces real light weight kernel threads which consume less low-level resources (process locks, memory maps). It also allows better grouping of threads for display purposes.
procstat(1): A process inspection utility
Status: Committed to -CURRENT
Will appear in 8.0: sure
Author: Robert Watson
Web: announcement
procstat combines functionality from the now-deprecated procfs(4) and adds several new functionalities. Some of the data procstat can provide are: process' command line arguments, file descriptor information, stacks of the kernel threads in the process, security credentials information from the process, thread information and virtual memory mappings. This is utility is mostly useful for debugging.
TextDumps: gathering information after kernel panic
Status: Committed to -CURRENT, MFC-ed to 7-STABLE
Will appear in 8.0: sure
Author: Robert Watson
Web: Q&A on textdumps
The usual thing that happens after a kernel panic is a kernel memory dump, either full or (in 7.0 and later) a "minidump". The new "textdump" feature doesn't store the actual kernel memory dump, but extracts commonly needed information from it, stores it into a tar archive of text files, and deletes the dump file. This significantly reduces the size requirements of collecting such information, speeds up development, and enables people to collect debugging information after a crash without kernel developer experience.
ULE 3.0: New version of the SMP-optimized scheduler
Status: Committed to -CURRENT
Will appear in 8.0: sure
Author: Jeff Roberson
Web: commit message,
commit message,
announcement
Evolution of the ULE scheduler resulted in support for fine-grained CPU affinity calculations, taking into account the physical topology of the CPUs (caches, cores, sockets) and much improved support for binding threads to CPUs. This results in additional functionalities (opens up the possibility of assigning individual CPUs to jails) and noticeable performance improvements.
Superpages
Status: Committed to -CURRENT
Will appear in 8.0: sure
Author Alan Coy
Web: research paper
Most general-purpose processors provide support for memory pages of large sizes, called superpages. Superpages enable each entry in the translation lookaside buffer (TLB) to map a large physical memory region into a virtual address space. This dramatically increases TLB coverage, reduces TLB misses, and promises performance improvements for many applications. However, supporting superpages poses several challenges to the operating system, in terms of superpage allocation and promotion tradeoffs, fragmentation control, etc. We analyze these issues, and propose the design of an effective superpage management system. We implement it in FreeBSD on the Alpha CPU, and evaluate it on real workloads and benchmarks. We obtain substantial performance benefits, often exceeding 30%; these benefits are sustained even under stressful workload scenarios.
For now, superpages are only available for AMD64 architecture (aka x86_64).
DTrace
Status: Committed to -CURRENT (kernel trace only)
Will appear in 8.0: sure
Author: John Birrell
Web: project web page
DTrace is a tool and a language developed by Sun Microsystems to help debugging and profiling operating systems. It can aggregate information from different parts of both kernel and userland and analyze them in a ways that's meaningful to the user.
Networking improvements
VirtNet / VIMAGE / Imunes / Network stack virtualization
Status: In final stages of development
Will appear in 8.0: sure
Author: Marko Zec
Web: project web page
The network stack virtualization project aims at extending the FreeBSD kernel to maintain multiple independent instances of networking state. This will allow for complete networking independence between jails on a system, including giving each jail its own firewall, virtual network interfaces, rate limiting, routing tables, and IPSEC configuration.
Multiple routing tables / FIBs
Status: Committed to 8-CURRENT
Will appear in 8.0: sure
Authors: Julian Elischer
Web: proposal
Support for multiple routing tables (forwarding information bases) allows advanced network topologies. The setfib utility can be used to select routing tables on per-process level.
Equal cost multipath routing
Status: Committed to 8-CURRENT
Will appear in 8.0: sure
Authors: Qing Li
Web: commit message
ECMP routing allows for multiple routes to be handled by the kernel, including default routes. It potentially offers substantial increases in bandwidth by load-balancing traffic over multiple paths.
Zero-copy BPF
Status: Committed to 8-CURRENT
Will appear in 8.0: sure
Authors: Robert Watson, Christian S.J. Peron
Web: BSDCan slides
BPF is Berkeley Packet Filter, facility used to capture raw network packets from the lower layers of the network stack according to user-defined filters and forward them to an application, as well as insert raw packets to the network stack.
This improvement to BPF reduces the number of memory copy operations between the kernel and the application which improves performance in some cases.
Kernel NFS locking support
Status: Committed to 8-CURRENT
Will appear in 8.0: sure
Author: Doug Rabson
Web: commit message,
announcement
NFS lock manager in kernel improves performance and behaviour of NFS locking (used to synchronize file access on remote machines). New features include multithreaded operation, deadlock detection, and transparent interaction with local file locks on the server.
Storage subsystems' improvements
Boot support for GPT partitions
Status: Committed to -CURRENT
Will appear in 8.0: sure
Author: John Baldwin
Web: commit message
Support for booting from GPT partitions has been committed to -CURRENT. This support includes the boot sector and loader that enable common i386 machines with a generic BIOS to boot from GPT-partitioned drives.
bsdlabel gets extended to 26 partitions
Status: Committed to -CURRENT
Will appear in 8.0: sure
Author: Marcel Moolenaar
Web: commit message
bsdlabel is (finally!) extended to support more than 8 partitions. The new limit of 26 partitions comes from the number of lower-case leters.
To make use of this change, GEOM_PART needs to be used instead of GEOM_BSD (this requires custom kernel configurations).
Other changes
- User-controllable CPU/IRQ binding (jhb)
- User-controllable CPU-thread binding with support for CPU sets (jeffr)
