Date: Wed, 2 Nov 2005 17:29:47 GMT From: Robert Watson <rwatson@FreeBSD.org> To: Perforce Change Reviews <perforce@freebsd.org> Subject: PERFORCE change 86239 for review Message-ID: <200511021729.jA2HTleT095807@repoman.freebsd.org>
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http://perforce.freebsd.org/chv.cgi?CH=86239 Change 86239 by rwatson@rwatson_zoo on 2005/11/02 17:29:20 When hinted not to preempt, also don't IPI. Affected files ... .. //depot/projects/netsmp/src/sys/kern/sched_4bsd.c#3 edit Differences ... ==== //depot/projects/netsmp/src/sys/kern/sched_4bsd.c#3 (text+ko) ==== @@ -1159,29 +1159,40 @@ cpu = NOCPU; ke->ke_runq = &runq; } - - if (single_cpu && (cpu != PCPU_GET(cpuid))) { - kick_other_cpu(td->td_priority,cpu); - } else { - - if (!single_cpu) { - cpumask_t me = PCPU_GET(cpumask); - int idle = idle_cpus_mask & me; + + /* + * Once we've established where to schedule the thread, we have to + * decide if we want to preempt the current thread, or IPI another + * CPU to start immediate execution there. + * + * Currently, suppressing preemption on the scheduling also + * suppresses IPIs to shedule on another CPU, as it is assumed that + * starting the thread running at once will result in poor timing of + * events, lock contention, etc. + */ + if (!(flags & SRQ_NOPREEMPT)) { + if (single_cpu && (cpu != PCPU_GET(cpuid))) { + kick_other_cpu(td->td_priority,cpu); + } else { + if (!single_cpu) { + cpumask_t me = PCPU_GET(cpumask); + int idle = idle_cpus_mask & me; - if (!idle && ((flags & SRQ_INTR) == 0) && - (idle_cpus_mask & ~(hlt_cpus_mask | me))) - forwarded = forward_wakeup(cpu); - } + if (!idle && ((flags & SRQ_INTR) == 0) && + (idle_cpus_mask & ~(hlt_cpus_mask | me))) + forwarded = forward_wakeup(cpu); + } - if (!forwarded) { - if ((flags & SRQ_YIELDING) == 0 && - (flags & SRQ_NOPREEMPT) == 0 && - maybe_preempt(td)) - return; - else - maybe_resched(td); + if (!forwarded) { + if ((flags & SRQ_YIELDING) == 0 && + maybe_preempt(td)) + return; + else + maybe_resched(td); + } } - } + } else + maybe_resched(td); if ((td->td_proc->p_flag & P_NOLOAD) == 0) sched_load_add();
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