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author | jhb <jhb@FreeBSD.org> | 2004-07-02 20:21:44 +0000 |
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committer | jhb <jhb@FreeBSD.org> | 2004-07-02 20:21:44 +0000 |
commit | 696704716d52a895094da20b7e1a0f763b069e12 (patch) | |
tree | 2a5d6a91ba98f5b9e075eecc1a9ca724b8a9110a /sys/conf | |
parent | 1f506bc6fab7cc97cb923d4af1174f9c732221dd (diff) | |
download | FreeBSD-src-696704716d52a895094da20b7e1a0f763b069e12.zip FreeBSD-src-696704716d52a895094da20b7e1a0f763b069e12.tar.gz |
Implement preemption of kernel threads natively in the scheduler rather
than as one-off hacks in various other parts of the kernel:
- Add a function maybe_preempt() that is called from sched_add() to
determine if a thread about to be added to a run queue should be
preempted to directly. If it is not safe to preempt or if the new
thread does not have a high enough priority, then the function returns
false and sched_add() adds the thread to the run queue. If the thread
should be preempted to but the current thread is in a nested critical
section, then the flag TDF_OWEPREEMPT is set and the thread is added
to the run queue. Otherwise, mi_switch() is called immediately and the
thread is never added to the run queue since it is switch to directly.
When exiting an outermost critical section, if TDF_OWEPREEMPT is set,
then clear it and call mi_switch() to perform the deferred preemption.
- Remove explicit preemption from ithread_schedule() as calling
setrunqueue() now does all the correct work. This also removes the
do_switch argument from ithread_schedule().
- Do not use the manual preemption code in mtx_unlock if the architecture
supports native preemption.
- Don't call mi_switch() in a loop during shutdown to give ithreads a
chance to run if the architecture supports native preemption since
the ithreads will just preempt DELAY().
- Don't call mi_switch() from the page zeroing idle thread for
architectures that support native preemption as it is unnecessary.
- Native preemption is enabled on the same archs that supported ithread
preemption, namely alpha, i386, and amd64.
This change should largely be a NOP for the default case as committed
except that we will do fewer context switches in a few cases and will
avoid the run queues completely when preempting.
Approved by: scottl (with his re@ hat)
Diffstat (limited to 'sys/conf')
-rw-r--r-- | sys/conf/NOTES | 6 | ||||
-rw-r--r-- | sys/conf/options | 1 |
2 files changed, 7 insertions, 0 deletions
diff --git a/sys/conf/NOTES b/sys/conf/NOTES index 2607142..f944152 100644 --- a/sys/conf/NOTES +++ b/sys/conf/NOTES @@ -186,6 +186,11 @@ options MUTEX_WAKE_ALL # SMP Debugging Options: # +# FULL_PREEMPTION instructs the kernel to preempt non-realtime kernel +# threads. It sole use is to expose race conditions and other +# bugs during development. Enabling this option will reduce +# performance and increase the frequency of kernel panics by +# design. If you aren't sure that you need it then you don't. # MUTEX_DEBUG enables various extra assertions in the mutex code. # SLEEPQUEUE_PROFILING enables rudimentary profiling of the hash table # used to hold active sleep queues. @@ -197,6 +202,7 @@ options MUTEX_WAKE_ALL # a lock hierarchy violation occurs or if locks are held when going to # sleep. # WITNESS_SKIPSPIN disables the witness checks on spin mutexes. +options FULL_PREEMPTION options MUTEX_DEBUG options WITNESS options WITNESS_DDB diff --git a/sys/conf/options b/sys/conf/options index d086703..2fb6582 100644 --- a/sys/conf/options +++ b/sys/conf/options @@ -61,6 +61,7 @@ DDB_NUMSYM opt_ddb.h DDB_TRACE DDB_UNATTENDED DIRECTIO opt_directio.h +FULL_PREEMPTION GDB_REMOTE_CHAT opt_ddb.h GDBSPEED opt_ddb.h GEOM_AES opt_geom.h |