From: Paul Thomas <pthomas8589@gmail.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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: Thu, 15 Aug 2019 14:00:34 -0400 [thread overview]
Message-ID: <CAD56B7fnVpmiE+m71zHSNuQw49GWJJ0ySGUD3Zc2mih_CxUjpg@mail.gmail.com> (raw)
In-Reply-To: <20190813095306.xqgq3uusdpj7dhy7@linutronix.de>
> could you please try the following hunk?
>
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index 6808cd9526c67..63c6960262861 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -648,7 +648,8 @@ alternative_if ARM64_HAS_IRQ_PRIO_MASKING
> orr x24, x24, x0
> alternative_else_nop_endif
>
> - cbnz x24, 2f // preempt count != 0
> + cbz x24, 1f // (need_resched + count) == 0
> + cbnz w24, 2f // count != 0
>
> ldr w24, [tsk, #TSK_TI_PREEMPT_LAZY] // get preempt lazy count
> cbnz w24, 2f // preempt lazy count != 0
>
After correctly applying this patch I do not see large latencies, >15M
iterations and counting.
# ./cyclictest -S -m -n -p 99 -i 200 -h 700 -f
# /dev/cpu_dma_latency set to 0us
policy: fifo: loadavg: 0.04 0.06 0.18 1/134 2043
T: 0 ( 1968) P:99 I:200 C:15081932 Min: 6 Act: 8 Avg: 7 Max: 22
T: 1 ( 1969) P:99 I:200 C:15081831 Min: 6 Act: 9 Avg: 7 Max: 17
T: 2 ( 1970) P:99 I:200 C:15081727 Min: 6 Act: 9 Avg: 8 Max: 17
T: 3 ( 1971) P:99 I:200 C:15081619 Min: 6 Act: 9 Avg: 8 Max: 18
I apologize for messing this up the first time. I had copied the text
strait from gmail and it failed to apply. If I had used 'patch -l' or
copied it from the archive, then it directly applies and I wouldn't
have messed up when I put it in manually. Just for reference here's
how I screwed it up:
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 6808cd9526c6..be0933a3f5e3 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -651,7 +651,8 @@ alternative_else_nop_endif
cbnz x24, 2f // preempt count != 0
ldr w24, [tsk, #TSK_TI_PREEMPT_LAZY] // get preempt
lazy count
- cbnz w24, 2f // preempt
lazy count != 0
+ cbz x24, 1f //
(need_resched + count) == 0
+ cbnz w24, 2f // count != 0
ldr x0, [tsk, #TSK_TI_FLAGS] // get flags
tbz x0, #TIF_NEED_RESCHED_LAZY, 2f // needs rescheduling?
thanks,
Paul
next prev parent reply other threads:[~2019-08-15 18:00 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
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 [this message]
2019-08-15 18:57 ` Sebastian Andrzej Siewior
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