From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Paul Thomas <pthomas8589@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
dunc.mcphie@gmail.com, Anders Roxell <anders.roxell@linaro.org>
Subject: Re: poor cyclictest results with 5.0 series rt for arm64
Date: Wed, 14 Aug 2019 13:26:56 +0200 [thread overview]
Message-ID: <20190814112656.z3de2rgbqzpaquz5@linutronix.de> (raw)
In-Reply-To: <CAD56B7fqosJAhiCLikhcxv_3wY7ETOv++kmQcr-=9NKEGq7Agw@mail.gmail.com>
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
next prev parent reply other threads:[~2019-08-14 11:27 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-12 11:18 poor cyclictest results with 5.0 series rt for arm64 Paul Thomas
[not found] ` <CAD56B7c2=95r7r-6tr0Mby8jSeuQPDNSd4LELnUw1LVRn9Rqew@mail.gmail.com>
2019-07-12 11:32 ` Paul Thomas
2019-07-16 20:24 ` Thomas Gleixner
2019-07-16 21:50 ` Paul Thomas
2019-07-16 23:14 ` Thomas Gleixner
2019-07-17 0:44 ` Paul Thomas
2019-07-17 8:03 ` Thomas Gleixner
2019-07-17 8:10 ` Thomas Gleixner
2019-07-17 9:02 ` Thomas Gleixner
2019-07-17 10:21 ` Thomas Gleixner
2019-07-17 22:28 ` Paul Thomas
2019-08-13 9:53 ` Sebastian Andrzej Siewior
2019-08-13 18:02 ` Paul Thomas
2019-08-14 11:26 ` Sebastian Andrzej Siewior [this message]
2019-08-14 16:17 ` [PATCH RT] arm64: preempt: Check preemption level before looking at lazy-preempt Sebastian Andrzej Siewior
2019-08-14 16:17 ` [PATCH RT] x86: " Sebastian Andrzej Siewior
2019-08-14 17:04 ` poor cyclictest results with 5.0 series rt for arm64 Paul Thomas
2019-08-15 8:29 ` Sebastian Andrzej Siewior
2019-08-15 12:33 ` John Ogness
2019-08-15 13:30 ` Paul Thomas
2019-08-15 13:42 ` Sebastian Andrzej Siewior
2019-08-15 13:52 ` Paul Thomas
2019-08-15 14:19 ` Sebastian Andrzej Siewior
2019-08-15 15:12 ` Paul Thomas
2019-08-15 15:15 ` Sebastian Andrzej Siewior
2019-08-15 15:31 ` Paul Thomas
2019-08-15 18:00 ` Paul Thomas
2019-08-15 18:57 ` Sebastian Andrzej Siewior
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