Improving performance on multiprocessor systems

Phase 1
Branches: yamt-splraiseipl, newlock2

MT safe sleep / wakeup
Modern locking primitives

Area Task Responsible Progress
Synchronisation primitives Implement new primitives. thorpej, ad Complete
Implement splraiseipl() yamt Complete
Implement profiling tool (lockstat). ad Complete
Process state Reorganise, lock and document necessary process and LWP state. ad Complete
Make signals MT and sleep safe. ad Complete
Make ktrace MT and sleep safe ad Complete
Branch work
Complete, test and merge newlock2 branch. All Complete
Implement MD stubs on architectures other than x86. All Complete

Phase 2
Branches: yamt-idlelwp, vmlocking

Fewer side effects when using locks
Allow MT safe and unsafe code to coexist
VM system and VFS made MT safe

Area Task Responsible Progress
Implement threaded soft interrupts. ad Complete
Retire spinlockmgr(). ad Complete
Make lockmgr() use mutexes for interlocking. ad Complete
Make callout_init() take a flags argument and push the kernel lock acquire down into softclock(). ad Complete
Implement a generic cross-call facility ad Complete
Scheduler Increase the number of available priority levels, maybe defining: user, system, real time and interrupt. ad Complete
Implement one idle LWP per CPU, and reduce cpu_switch() to cpu_switchto() yamt, all Complete
Remove MD setrunqueue()/remrunqueue(). yamt Complete
Support per-CPU run queues to reduce contention and facilitate bound LWPs. ad, rmind Complete
Implement priority inheritance for turnstiles. yamt Complete
Device drivers Put wrappers around the devsw entry points that will take the kernel lock for MT unsafe drivers. ad Complete
Misc Make x86 use MONITOR/MWAIT to obviate need for IPIs when waking other CPUs. yamt Complete
VM system In UVM, replace simple_lock and lockmgr locks with mutexes and rwlocks. ad Complete
Profile and improve concurrency. ad Complete
Implement per-CPU caching allocator. ad, yamt Complete
Replace locks in other components, eg: pools, malloc, vmem. ad Complete
In the PMAP modules, replace simple_lock and lockmgr locks. ad Complete
Solve any documented races and and locking problems in UVM. ad, yamt Complete
VFS Make the ufs/tmpfs/other file systems MT safe ad Complete
Push the kernel_lock back into VOP_ wrappers and file operation sets ad Complete
Update the VFS locking scheme to be more MT friendly where necessary ad Complete

Phase 3
Branches: HEAD

Work to complete before release of NetBSD 5.0

Area Task Responsible Progress
Compat code Nuke the stackgap dsl Complete
Update compat code to be MT safe, or nuke where appropriate ad, dsl Complete
Device drivers Make kqueue MT safe ad Complete
Overhaul select/poll to use per thread state, and to cache state ad, rmind Complete
Networking Remove kernel_lock from Unix domain sockets ad Complete
Allow network soft interrupt handlers to block. ad Complete
Process state Join interrupt and process context locks, so that the only remaining interrupt context locks are on objects intimately related to the scheduler (e.g. LWPs, run queues). Requires threaded soft interrupts, and allowing network ISRs to block. ad Complete
Full per-LWP stats (eg rusage). ad Complete
POSIX threads Implement adaptive mutexes ad Complete
VFS Improve concurrency in the file system name cache ad Complete

Future work
Branches: HEAD

Area Task Responsible Progress
Primitives Replace uses of simple locks and lockmgr() locks throughout the kernel. All Underway
Implement a patent free alternative to RCU (read, copy, update) ad Underway
Device drivers Allow interrupt handlers to be individually marked as MT safe / unsafe. ? None
Lock the SCSIPI subsystem. ? None
Lock the ATA subsystem. ? None
Lock RAIDframe. ? None
Profiling Make lockstat use timecounters for reporting, so that results are accurate for sleep locks ? None
Make event counters lockless. ? None
Convert remaining global counters into event counters. ? None