272 lines
10 KiB
Plaintext
272 lines
10 KiB
Plaintext
$NetBSD: system,v 1.4 2008/03/21 08:53:06 spz Exp $
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NetBSD System Roadmap
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=====================
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This is a small roadmap document, and deals with the main system
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aspects of the operating system.
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NetBSD 5.0 will ship with the following main changes to the system:
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1. Modularized scheduler
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2. Real-time scheduling classes and priorities
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3. Processor sets, processor affinity and processor control
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4. Multiprocessor optimized scheduler
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5. High-performance 1:1 threading implementation
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6. Pushback of the global kernel lock
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7. New kernel concurrency model
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8. Multiprocessor optimized memory allocators
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9. POSIX asynchronous I/O and message queues
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10. In-kernel linker
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11. SysV IPC tuneables
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12. Improved observability: minidumps, lockstat and tprof
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13. Power management framework
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We are working on the following elements, and expect them to be in 5.0:
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14. Full kernel preemption for real-time threads
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15. 64-bit time values supported
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16. POSIX shared memory
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17. namei() tactical changes
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The following projects are expected to be included in NetBSD 6.0
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18. Better resource controls
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19. Improved observability: online crashdumps, remote debugging
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20. Processor and cache topology aware scheduler
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We expect to branch for the 5.0 release in April or May 2008, which would
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put a NetBSD 5.0 Release date in Q4 2008. An annual release cycle would
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thus mean that 6.0 would be branched in April or May 2009.
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Pictorially, this looks like:
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2008 2009
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Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug
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|===|===|===|===|===|===|===|===|===|===|===|===|===|===|===|===|===|===|===|
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| ------- 5.0 --------- | | ------- 6.0
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branch release branch
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1-8 11,15-17,18 9,10,12-14 19 20
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We'll continue to update this roadmap as features and dates get firmed up.
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Some explanations
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=================
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1. Modularized scheduler
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------------------------
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Traditionally the only method of control on process scheduling was the
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'nice' value assigned to each process. The scheduler interface has been
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redesiged to allow for pluggable schedulers, selected at compile time.
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At the current time, there are no plans to switch schedulers at run-time,
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since there is little appreciable gain to be had from that, and the extra
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performance hit to provide this functionality is thought not to be worth
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it.
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The in-kernel scheduler interface has been enhanced to provide a framework
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for adding new schedulers, called the common scheduler framework - more
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information can be found in the csf(9) manual page.
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Responsible: ad, dsieger, rmind, yamt
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2. Real-time scheduling classes and priorities
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----------------------------------------------
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The scheduler has been extended to allow provide multiple new priority
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bands, including real-time. POSIX standard interfaces for controlling
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thread priority and scheduling class have been implemented, along with
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a command line tool to allow control by the system administrator.
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3. Processor sets, processor affinity and processor control
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-----------------------------------------------------------
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A Solaris and HP-UX compatible interface for defining and controlling
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processor sets has been added. Processor sets allow applications and
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the administrator complete flexibility in partitioning CPU resources
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among applications, down to thread-level granularity.
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Linux compatibile interface controlling processor affinity, similar
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in spirit to processor sets, is provided.
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A new utility to control CPU status (cpuctl) is provided. cpuctl
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allows the administrator to enable and disable individual CPUs at
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the software level, while the system is running. It is expected that
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this will in time be extended to support full dynamic reconfiguration,
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in concert with a hypervisor such as Xen.
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4. Multiprocessor optimized scheduler
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-------------------------------------
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An intelligent, pluggable scheduler named M2 that is optimized for
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multiprocessor systems, supports POSIX real-time extensions,
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time-sharing class, and implements thread affinity.
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5. High-performance 1:1 threading implementation
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------------------------------------------------
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A new lightweight 1:1 threading implementation, replacing the M:N based
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implementation found in NetBSD 4.0 and earlier. The new implementation is
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more correct according to POSIX thread standards, and provides a massive
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performance boost to threaded workloads in both uni- and multi-processor
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configurations.
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6. Pushback of the global kernel lock
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-------------------------------------
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Previously, most access to the kernel was single threaded on multiprocessor
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systems by the global kernel_lock. The kernel_lock has been pushed back to
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to the device driver and wire-protocol layers, providing a significant
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performance boost on heavily loaded multiprocessor systems.
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7. New kernel concurrency model
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-------------------------------
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The non-preemptive spinlock and "interrupt priority level" synchronization
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model has been replaced wholesale with a hybrid thread/interrupt model. A
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full range of new, lightweight synchronization primitives are available to
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the kernel programmer, including: adaptive mutexes, reader/writer locks,
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memory barriers, atomic operations, threaded soft interrupts, generic cross
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calls, workqueues, priority inheritance, and per-CPU storage.
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8. Multiprocessor optimized memory allocators
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---------------------------------------------
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The memory allocators in both the kernel and user space are now fully
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optimized for multiprocessor systems and eliminate the performance
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degradation typically associated with memory allocators in an MP setting.
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9. POSIX asynchronous I/O and message queues
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---------------------------------------------
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A full implementation of the POSIX asynchronous I/O and message
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queue facilities is now available.
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10. In-kernel linker
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--------------------
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A in-kernel ELF object linker has been added, and a revamped kernel module
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infrastructure developed to accompany it. It is expected that the kernel
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will become completely modular over time, while continuing to retain the
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ability to link to a single binary image for embedded and hobby systems.
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11. SysV IPC tuneables
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----------------------
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Parameters for the SVR3-compatible IPC mechanisms can now be tuned
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completely at runtime.
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12. Improved observability: minidumps, lockstat and tprof
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---------------------------------------------------------
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The x86 architecture now supports mini crash-dumps as a support aid for
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kernel debugging. Only memory contents actively in use by the kernel at
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the time of crash are dumped to and recovered from disk, an improvement
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over the traditional scheme where the complete contents of memory is
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dumped to disk.
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The lockstat and tprof commands have been addded to the system. lockstat
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provides a high-resolution description of lock activity in a running system.
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tprof uses sample based profiling in conjuction with the available
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performance counters in order to better profile system activity.
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13. Power management framework
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------------------------------
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A new power management framework has been introduced that improves
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handling of device power state transitions. As power management support
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is now integrated with the auto-configuration subsystem, the kernel can
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ensure that a parent device is powered on before attempting to access
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the device.
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With these changes comes an updated release of the Intel ACPI
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Component Architecture and an x86 emulator which assists in restoring
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uninitialized display adapters.
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Leveraging this work, the i386 and amd64 kernels now support suspend
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to RAM in uni- and multi-processor configurations on ACPI-capable
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machines. This support has been successfully tested on a wide variety of
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laptops, including (but not limited to) recent systems from Dell, IBM/Lenovo,
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Fujitsu, Toshiba, and Sony.
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Responsible: jmcneill, joerg
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14. Full kernel preemption for real-time threads
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------------------------------------------------
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With the revamp of the kernel concurrency model, much of the kernel is fully
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multi-threaded and can therefore be preempted at any time. In support of
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lower context switch and dispatch times for real-time threads, full kernel
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preemption is being implemented.
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15. 64-bit time_t support
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-------------------------
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The Unix 32-bit time_t value will overflow in 2037 - any mortgage calculations
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which use a time_t value are in danger of overflowing at the present time -
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and to address this, 64-bit time_t values will be used to contain the number
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of seconds since 1970.
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Responsible: christos
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16. POSIX shared memory
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-----------------------
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Implement POSIX shared memory facilities, which can be used to create the
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shared memory objects and add the memory locations to the address space of
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a process.
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Responsible: rmind
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17. Incremental namei improvements, Phase 1
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-------------------------------------------
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Implement the rest of the changes to namei outlined in Message-ID:
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<20080319053709.GB3951@netbsd.org>. Simplify the locking and behavior
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of namei() calls within the kernel to resolve path names within file
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systems. This phase simplifies the majority of calls to namei().
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Responsible: dholland
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18. Better resource controls
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----------------------------
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A resource provisioning and control framework that extends beyond the
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traditional Unix process limits.
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19. Improved observability: online crashdumps, remote debugging
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---------------------------------------------------------------
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XXX crashdumps while the system is running
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XXX firewire support in libkvm
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20. Processor and cache topology aware scheduler
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------------------------------------------------
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Implement the detection of the topology of the processors and caches.
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Improve the scheduler to make decisions about thread migration
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according to the topology, to get better thread affinity and less
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cache thrashing, and thus improve overall performance in modern SMP
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systems.
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Responsible: rmind
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29. Incremental namei improvements, Phase 2
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-------------------------------------------
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Implement the rest of the changes to namei outlined in Message-ID:
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<20080319053709.GB3951@netbsd.org>. Simplify the locking and behavior
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of namei() calls within the kernel to resolve path names within file
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systems.
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Responsible: dholland
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Andrew Doran
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Wed Mar 19 18:26:49 GMT 2008
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