On Wed, Aug 14, 2019 at 7:26 AM Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote: > > On 2019-08-13 14:02:39 [-0400], Paul Thomas wrote: > > I still get large latencies, like this: > > root@xu5:/opt/rt-tests# ./cyclictest -h ./cyclictest -S -m -n -p 99 -i > > 200 -h 400 -D 900 > > # /dev/cpu_dma_latency set to 0us > > policy: fifo: loadavg: 0.10 0.10 0.03 1/134 1901 > > > > T: 0 ( 1886) P:99 I:200 C:2724618 Min: 5 Act: 6 Avg: 6 Max: 45 > > T: 1 ( 1887) P:99 I:200 C:2724525 Min: 5 Act: 7 Avg: 6 Max: 29 > > T: 2 ( 1888) P:99 I:200 C:2724246 Min: 5 Act: 6 Avg: 6 Max: 6338 > > T: 3 ( 1889) P:99 I:200 C:2724339 Min: 5 Act: 8 Avg: 6 Max: 141 > > > > This is with the Lazy preempt commit in there. > > I re-read the thread and figured out that you talk about 5.0 while I was > testing on 5.2. On my ARM64 box I end up with > > |T: 0 ( 9577) P:99 I:250 C:19979015 Min: 3 Act: 4 Avg: 3 Max: 19 > |T: 1 ( 9578) P:99 I:250 C:19978958 Min: 3 Act: 3 Avg: 3 Max: 24 > |T: 2 ( 9579) P:99 I:250 C:19978901 Min: 3 Act: 4 Avg: 4 Max: 22 > |T: 3 ( 9580) P:99 I:250 C:19978843 Min: 3 Act: 3 Avg: 3 Max: 19 > > with the patch I sent you. Without it, had spikes between 130us and > 160us. Since you said it is not working, I looked more and came up with > this: > > diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h > index 3bfad251203b5..ca1c6fe8dd347 100644 > --- a/arch/arm64/include/asm/preempt.h > +++ b/arch/arm64/include/asm/preempt.h > @@ -73,6 +73,8 @@ static inline bool __preempt_count_dec_and_test(void) > if (!pc || !READ_ONCE(ti->preempt_count)) > return true; > #ifdef CONFIG_PREEMPT_LAZY > + if ((pc & ~PREEMPT_NEED_RESCHED)) > + return false; > if (current_thread_info()->preempt_lazy_count) > return false; > return test_thread_flag(TIF_NEED_RESCHED_LAZY); > > but this shouldn't make any difference for you (but it is a bug fix). > Staring more into it, I don't see anything wrong. > > v5.0 is not supported any more. Do you think, that you could re-test on > 5.2-RT with those two patches I sent you? Hi Sebastian, Yes, for the test yesterday it was using 5.2.0-rt1, I should have explained that in the first response, since I posted this we have moved to 5.2. I added the second patch as well and it was still happening. I took another trace data set in case this is helpful. I added an attachment to the bugzilla bug: https://bugzilla.kernel.org/show_bug.cgi?id=204189 The attachment is here: https://bugzilla.kernel.org/attachment.cgi?id=284391 We don't actually need Lazy Preempt, so now that we know what the issues is we can just turn it off in the config? However I suspect everyone wants to get to the bottom of what's going on at this point? thanks, Paul
