Messages in this thread | | | Date | Sat, 14 Aug 2004 13:19:45 +0100 | From | James Courtier-Dutton <> | Subject | Re: [patch] Latency Tracer, voluntary-preempt-2.6.8-rc4-O6 |
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This is just for info, now that we have a nice latency testing tool, we might as well collect some useful traces that we can later work on.
Here is a trace showing a latency of 39034us. http://www.superbug.demon.co.uk/kernel/
The interesting parts of it are: 0.002ms (+0.000ms): __preempt_spin_lock (schedule) 0.523ms (+0.520ms): do_IRQ (common_interrupt) ... 0.532ms (+0.000ms): end_edge_ioapic_irq (do_IRQ) 0.763ms (+0.230ms): smp_apic_timer_interrupt (apic_timer_interrupt) ... 0.768ms (+0.000ms): preempt_schedule (try_to_wake_up) 1.523ms (+0.754ms): do_IRQ (common_interrupt) ... 1.533ms (+0.000ms): __do_softirq (do_softirq) 1.763ms (+0.229ms): smp_apic_timer_interrupt (apic_timer_interrupt) ... 1.765ms (+0.000ms): __do_softirq (do_softirq) 2.523ms (+0.757ms): do_IRQ (common_interrupt) ... 2.533ms (+0.000ms): do_softirq (do_IRQ) 2.533ms (+0.000ms): __do_softirq (do_softirq) 2.763ms (+0.230ms): smp_apic_timer_interrupt (apic_timer_interrupt) ...
This looks to me to be a bug somewhere. Either in the O7 patch, or in the kernel. Surely, do_IRQ should happen quickly, and not take 39ms.
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