From: Tim Sander <tim@krieglstein.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-rt-users <linux-rt-users@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
rostedt@goodmis.org, John Kacur <jkacur@redhat.com>
Subject: Re: [ANNOUNCE] 4.1.5-rt5 meant to reply to 4.4.1-rt5
Date: Fri, 12 Feb 2016 15:36:16 +0100 [thread overview]
Message-ID: <7138155.u6nNkmxGuH@dabox> (raw)
In-Reply-To: <56BDA0EF.7090503@linutronix.de>
Hi Sebastian
As you got correctly i was talking about 4.4.1-rt5 and not 4.1 i replied to by
accident.
Am Freitag, 12. Februar 2016, 10:07:59 schrieb Sebastian Andrzej Siewior:
> On 02/12/2016 09:28 AM, Tim Sander wrote:
> > Hi Sebastian
>
> Hi Tim,
>
> > Am Sonntag, 16. August 2015, 15:56:30 schrieb Sebastian Andrzej Siewior:
> >> I'm pleased to announce the v4.1.5-rt5 patch set.
> >
> > I have just tested it with a Altera SoC ARM v7. The latencies seem to have
> > gotten a little bit worse with each release. The first core has always
> > been
> > worse (presumably due to interrupt load) but now it dropped to 111µs (rt5)
> > from 76µs(rt3) and 54µs(rt2).
>
> in -rt2 we had bug in migrate disable code which means each task was
> running on CPU0. This got partly fixed in -rt3. In -rt3 the scheduler
> could assign a task to CPU1 but the task should stay there for ever.
> This little detail was fixed in -rt5.
> This is one thing that comes to mind.
> Lazy-preempt should have been fixed in -rt3, too. This should not give
> you higher latencies but higher throughput.
>
> What about rt4? It is only the stable update so you should see here the
> numbers from rt3. If that is true and your numbers are stable it should
> be easy to run git bisect between rt4 and rt5. And looking at
> https://git.kernel.org/rt/linux-rt-devel/h/v4.4.1-rt5
> the only non-cosmetic change in -rt5 that should affect you is the
> migrate-disable fixup from Mike.
Ok, each run takes a couple of hours so bisecting should take quite some time
but i will give it a try. I started a test with 4.4.1-rt4, if the numbers are
within the 70µs ballpark bisecting seems the way to go. If the numbers are
higher i suspect that stable update might have a play here. But we will see.
Best regards
Tim
next prev parent reply other threads:[~2016-02-12 14:36 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-16 13:56 [ANNOUNCE] 4.1.5-rt5 Sebastian Andrzej Siewior
2016-02-12 8:28 ` Tim Sander
2016-02-12 9:07 ` Sebastian Andrzej Siewior
2016-02-12 14:36 ` Tim Sander [this message]
2016-02-17 8:14 ` Bisect results for 4.4.1-rt[4,5] Tim Sander
2016-02-25 14:06 ` Sebastian Andrzej Siewior
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