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? > thanks, > Paul Sebastian
