On Thu, Oct 08, 2009 at 08:23:37PM +0200, Mike Galbraith wrote: > On Thu, 2009-10-08 at 16:55 +0200, Frans Pop wrote: > > On Thursday 08 October 2009, Arjan van de Ven wrote: > > > From: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx> > > > Date: Thu, 24 Sep 2009 13:24:16 +0200 > > > Subject: [PATCH] x86, timers: check for pending timers after (device) > > > interrupts > > > > > > Now that range timers and deferred timers are common, I found a > > > problem with these using the "perf timechart" tool. > > > > > > It turns out that on x86, these two 'opportunistic' timers only > > > get checked when another "real" timer happens. > > > These opportunistic timers have the objective to save power by > > > hitchhiking on other wakeups, as to avoid CPU wakeups by themselves > > > as much as possible. > > > > This patch makes quite a difference for me. iwlagn and phy0 now > > consistently show at ~10 ms or lower. > > > > I do still get occasional high latencies, but those are for things like > > "[rpc_wait_bit_killable]" or "Writing a page to disk", where I guess you'd > > expect them. Those high latencies are mostly only listed for "Global" and > > don't translate to individual processes. > > I still see very high latencies coming out of idle (last noted was > > 300ms, NO_HZ) with this patch, and wonder if the hunk below makes any > difference whatsoever for you. Here, it definitely does. (shouldn't) I'm also seeing these strange, very high latencies here. Your patch didn't help unfortunately. This is from an otherwise idle NO_NZ system: # ./perf sched latency ----------------------------------------------------------------------------------------- Task | Runtime ms | Switches | Average delay ms | Maximum delay ms | ----------------------------------------------------------------------------------------- ksoftirqd/0:4 | 2.216 ms | 170 | avg: 24.235 ms | max: 808.356 ms | ksoftirqd/1:6 | 2.611 ms | 205 | avg: 4.334 ms | max: 165.553 ms | migration/2:7 | 0.000 ms | 1 | avg: 3.060 ms | max: 3.060 ms | With latencytop the ksoftirqd latency is over 1 sec frequently. (Could be ondemand CPUfreq governor related?) -- Markus -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
