From: John Stultz <jstultz@google.com>
To: Qais Yousef <qais.yousef@arm.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
John Dias <joaodias@google.com>,
"Connor O'Brien" <connoro@google.com>,
Rick Yiu <rickyiu@google.com>, John Kacur <jkacur@redhat.com>,
Chris Redpath <chris.redpath@arm.com>,
Abhijeet Dharmapurikar <adharmap@quicinc.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
kernel-team@android.com, "J . Avila" <elavila@google.com>
Subject: Re: [RFC PATCH v4 3/3] softirq: defer softirq processing to ksoftirqd if CPU is busy with RT
Date: Mon, 17 Oct 2022 17:04:09 -0700 [thread overview]
Message-ID: <CANDhNCo6M8NdLemjhA2sQ941agU+LQHxhRKAVMvr-qg9mQV51Q@mail.gmail.com> (raw)
In-Reply-To: <20221017144455.ylmwlgrdoj3tdvbp@wubuntu>
On Mon, Oct 17, 2022 at 7:45 AM Qais Yousef <qais.yousef@arm.com> wrote:
> This time I paid attention to the average as the best case number for vanilla
> kernel is better:
>
> | vanilla | with softirq patches v4 |
> -------------------|--------------------|--------------------------|
> | #1 | #2 | #3 | #1 | #2 | #3 |
> -------------------|------|------|------|--------|--------|--------|
> t0 avg delay (us) |31.59 |22.94 |26.50 | 31.81 | 33.57 | 34.90 |
> t1 avg delay (us) |16.85 |16.32 |37.16 | 29.05 | 30.51 | 31.65 |
> t2 avg delay (us) |25.34 |32.12 |17.40 | 26.76 | 28.28 | 28.56 |
>
> It shows that we largely hover around 30us with the patches compared to 16-26us
> being more prevalent for vanilla kernels.
>
> I am not sure I can draw a concrete conclusion from these numbers. It seems
> I need to run longer than 4 hours to hit the worst case scenario every run on
> the vanilla kernel. There's an indication that the worst case scenario is
> harder to hit, and it looks there's a hit on the average delay.
Thanks so much for running these tests and capturing these detailed numbers!
I'll have to look further into the average case going up here.
> I'm losing access to this system from today. I think I'll wait for more
> feedback on this RFC; and do another round of testing for longer periods of
> time once there's clearer sense this is indeed the direction we'll be going
> for.
Do you mind sending me the script you used to run the test, and I'll
try to reproduce on some x86 hardware locally?
thanks
-john
next prev parent reply other threads:[~2022-10-18 0:04 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-03 23:20 [RFC PATCH v4 0/3] Softirq -rt Optimizations John Stultz
2022-10-03 23:20 ` [RFC PATCH v4 1/3] softirq: Add generic accessor to percpu softirq_pending data John Stultz
2022-10-03 23:20 ` [RFC PATCH v4 2/3] sched: Avoid placing RT threads on cores handling long softirqs John Stultz
[not found] ` <20221004013611.1822-1-hdanton@sina.com>
2022-10-04 2:29 ` John Stultz
[not found] ` <20221005002149.1876-1-hdanton@sina.com>
2022-10-05 1:13 ` John Stultz
[not found] ` <20221005060155.1571-1-hdanton@sina.com>
2022-10-10 15:42 ` Qais Yousef
[not found] ` <20221011111846.284-1-hdanton@sina.com>
2022-10-12 14:10 ` Qais Yousef
2022-10-17 12:40 ` [PATCH RFC " Alexander Gordeev
2022-10-18 3:42 ` John Stultz
2022-10-18 3:59 ` John Stultz
2022-10-18 5:32 ` John Stultz
2022-10-19 9:11 ` Alexander Gordeev
2022-10-19 22:09 ` John Stultz
2022-10-20 0:15 ` Qais Yousef
2022-10-20 12:47 ` Alexander Gordeev
2022-10-22 18:34 ` Joel Fernandes
2022-10-23 7:45 ` Alexander Gordeev
2022-11-15 7:08 ` John Stultz
2022-11-15 12:55 ` Alexander Gordeev
2022-10-19 11:23 ` Qais Yousef
2022-10-22 18:28 ` [RFC PATCH " Joel Fernandes
2022-11-15 21:36 ` John Stultz
2022-10-03 23:20 ` [RFC PATCH v4 3/3] softirq: defer softirq processing to ksoftirqd if CPU is busy with RT John Stultz
2022-10-04 10:45 ` David Laight
2022-10-04 19:19 ` John Stultz
2022-10-10 16:09 ` Qais Yousef
2022-10-17 14:44 ` Qais Yousef
2022-10-18 0:04 ` John Stultz [this message]
2022-10-19 11:01 ` Qais Yousef
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