Date: Sat, 3 Jul 2004 17:56:49 -0400 (EDT) From: Robert Watson <rwatson@FreeBSD.org> To: John Baldwin <jhb@FreeBSD.org> Cc: cvs-all@FreeBSD.org Subject: FYI: SCHED_ULE broken with change (Re: HEADSUP: Native preemption added to the kernel scheduler) Message-ID: <Pine.NEB.3.96L.1040703175540.24282F-100000@fledge.watson.org> In-Reply-To: <200407021721.52787.jhb@FreeBSD.org>
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John may well be in transit or away for the holiday weekend. I'll try to take look at this issue tonight. As a work-around, it appears to be possible to run with SCHED_4BSD. (Or run without the change :-). Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Principal Research Scientist, McAfee Research On Fri, 2 Jul 2004, John Baldwin wrote: > In theory this is a big NOP except for some small optimizations in the form of > avoiding a few context switches and avoiding some run queue operations. > Several people have tested this code but there may be some remaining > adventures. Note that this adds a printf during dmesg for architectures that > do not support preemption about preemption being disabled and degrading > performance (mostly via increased latency). Preemption is enabled by > defining PREEMPTION in <machine/param.h> and architecture porters are > encouraged to get preemption working on their architecture. > > On Friday 02 July 2004 04:21 pm, John Baldwin wrote: > > jhb 2004-07-02 20:21:44 UTC > > > > FreeBSD src repository > > > > Modified files: > > sys/alpha/alpha interrupt.c > > sys/alpha/include param.h > > sys/amd64/amd64 intr_machdep.c > > sys/amd64/include param.h > > sys/conf NOTES options > > sys/i386/i386 intr_machdep.c > > sys/i386/include param.h > > sys/ia64/ia64 interrupt.c > > sys/kern kern_intr.c kern_mutex.c kern_shutdown.c > > kern_switch.c kern_synch.c sched_4bsd.c > > sched_ule.c > > sys/powerpc/powerpc intr_machdep.c > > sys/sparc64/sparc64 intr_machdep.c > > sys/sys interrupt.h proc.h > > sys/vm vm_zeroidle.c > > Log: > > 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) > > > > Revision Changes Path > > 1.79 +1 -1 src/sys/alpha/alpha/interrupt.c > > 1.34 +2 -0 src/sys/alpha/include/param.h > > 1.7 +1 -1 src/sys/amd64/amd64/intr_machdep.c > > 1.12 +2 -0 src/sys/amd64/include/param.h > > 1.1240 +6 -0 src/sys/conf/NOTES > > 1.459 +1 -0 src/sys/conf/options > > 1.7 +1 -1 src/sys/i386/i386/intr_machdep.c > > 1.71 +2 -0 src/sys/i386/include/param.h > > 1.46 +1 -1 src/sys/ia64/ia64/interrupt.c > > 1.111 +3 -16 src/sys/kern/kern_intr.c > > 1.140 +6 -0 src/sys/kern/kern_mutex.c > > 1.153 +24 -13 src/sys/kern/kern_shutdown.c > > 1.68 +93 -4 src/sys/kern/kern_switch.c > > 1.252 +4 -1 src/sys/kern/kern_synch.c > > 1.43 +11 -1 src/sys/kern/sched_4bsd.c > > 1.110 +10 -1 src/sys/kern/sched_ule.c > > 1.6 +1 -1 src/sys/powerpc/powerpc/intr_machdep.c > > 1.19 +0 -4 src/sys/sparc64/sparc64/intr_machdep.c > > 1.28 +1 -1 src/sys/sys/interrupt.h > > 1.384 +2 -0 src/sys/sys/proc.h > > 1.26 +2 -0 src/sys/vm/vm_zeroidle.c > > -- > John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ > "Power Users Use the Power to Serve" = http://www.FreeBSD.org > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" >
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