Date: Fri, 01 Oct 2004 01:23:21 -0400 From: Stephan Uphoff <ups@tree.com> To: John Baldwin <jhb@FreeBSD.org> Cc: "freebsd-arch@freebsd.org" <freebsd-arch@FreeBSD.org> Subject: Re: scheduler (sched_4bsd) questions Message-ID: <1096608201.21577.203.camel@palm.tree.com> In-Reply-To: <1096603981.21577.195.camel@palm.tree.com> References: <1095468747.31297.241.camel@palm.tree.com> <1096477932.3733.1471.camel@palm.tree.com> <1096489576.3733.1868.camel@palm.tree.com> <200409291652.29990.jhb@FreeBSD.org> <1096496057.3733.2163.camel@palm.tree.com> <1096603981.21577.195.camel@palm.tree.com>
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--=-fjzIiysJoZMWtL83qsgh Content-Type: text/plain Content-Transfer-Encoding: 7bit On Fri, 2004-10-01 at 00:13, Stephan Uphoff wrote: > I also had overlooked > http://www.holm.cc/stress/log/cons80.html > Showing that my patch for kern_switch.c (switch_patch) has a bug. > I will send an updated patch later today. OK - here is the promised patch. --=-fjzIiysJoZMWtL83qsgh Content-Disposition: attachment; filename=switch_patch_v2 Content-Type: text/x-patch; name=switch_patch_v2; charset=ASCII Content-Transfer-Encoding: 7bit Index: kern_switch.c =================================================================== RCS file: /cvsroot/src/sys/kern/kern_switch.c,v retrieving revision 1.95 diff -u -r1.95 kern_switch.c --- kern_switch.c 19 Sep 2004 18:34:17 -0000 1.95 +++ kern_switch.c 1 Oct 2004 05:15:16 -0000 @@ -315,6 +315,106 @@ td->td_priority = newpri; setrunqueue(td, SRQ_BORING); } + + +/* + * This function is called when a thread is about to be put on a + * ksegrp run queue because it has been made runnable or its + * priority has been adjusted and the ksegrp does not have a + * free kse slot. It determines if a thread from the same ksegrp + * should be preempted. If so, it tries to switch threads + * if the thread is on the same cpu or notifies another cpu that + * it should switch threads. + */ + +static void +maybe_preempt_in_ksegrp(struct thread *td) +{ +#if defined(SMP) + int highest_pri; + struct ksegrp *kg; + cpumask_t cpumask,dontuse; + struct pcpu *pc; + struct pcpu *highest_pcpu; + struct thread *running_thread; + +#ifndef FULL_PREEMPTION + int pri; + + pri = td->td_priority; + + if (!(pri >= PRI_MIN_ITHD && pri <= PRI_MAX_ITHD)) + return; +#endif + + mtx_assert(&sched_lock, MA_OWNED); + + running_thread = curthread; + +#if !defined(KSEG_PEEMPT_BEST_CPU) + if(running_thread->td_ksegrp != td->td_ksegrp) +#endif + { + kg = td->td_ksegrp; + + /* Anyone waiting in front ? */ + if(td != TAILQ_FIRST(&kg->kg_runq)) { + return; /* Yes - wait your turn*/ + } + highest_pri = td->td_priority; + highest_pcpu = NULL; + dontuse = stopped_cpus | idle_cpus_mask; + + /* Find a cpu with the worst priority that runs at thread from the + * same ksegrp - if multiple exist give first the last run cpu and then + * the current cpu priority + */ + + SLIST_FOREACH(pc, &cpuhead, pc_allcpu) { + cpumask = pc->pc_cpumask; + if ( (cpumask & dontuse) == 0 && + pc->pc_curthread->td_ksegrp == kg) { + if (pc->pc_curthread->td_priority > highest_pri) { + highest_pri = pc->pc_curthread->td_priority; + highest_pcpu = pc; + } else if (pc->pc_curthread->td_priority == highest_pri && + highest_pcpu != NULL) { + if (td->td_lastcpu == pc->pc_cpuid || + (PCPU_GET(cpumask) == cpumask && + td->td_lastcpu != highest_pcpu->pc_cpuid)) { + highest_pcpu = pc; + } + } + } + } + + /* Check if we need to preempt someone */ + if (highest_pcpu == NULL) return; + + if (PCPU_GET(cpuid) != highest_pcpu->pc_cpuid) { + highest_pcpu->pc_curthread->td_flags |= TDF_NEEDRESCHED; + ipi_selected(highest_pcpu->pc_cpumask, IPI_AST); + return; + } + } +#else + KASSERT(running_thread->td_ksegrp == td->td_ksegrp,("maybe_preempt_in_ksegrp: No chance to run thread")); +#endif + + if (td->td_priority > running_thread->td_priority) + return; +#ifdef PREEMPTION + if (running_thread->td_critnest > 1) { + running_thread->td_pflags |= TDP_OWEPREEMPT; + } else { + mi_switch(SW_INVOL, NULL); + } +#else + running_thread->td_flags |= TDF_NEEDRESCHED; +#endif + return; +} + int limitcount; void setrunqueue(struct thread *td, int flags) @@ -422,6 +522,7 @@ } else { CTR3(KTR_RUNQ, "setrunqueue: held: td%p kg%p pid%d", td, td->td_ksegrp, td->td_proc->p_pid); + maybe_preempt_in_ksegrp(td); } } --=-fjzIiysJoZMWtL83qsgh--
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