2014-06-19 15:11:23

by tdjames

Subject: How to disable Lazy Preempt in the kernel

I'm relatively new to Linux and working on getting a real-time kernel up and
running for robot applications. I'm on Ubuntu 14.04, using kernel 3.14.3 and
the 3.14.3-rt5 real-time patch. Also using x86-64.

There's a known error where the whole system crashes under some load when
lazy preempt is enabled. This has happened to me a few times now. My
question is:

How do I disable lazy preempt?

Thanks for the help!

-Tom



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2014-06-19 15:20:15

by Martin Steigerwald

Subject: Re: How to disable Lazy Preempt in the kernel

Am Donnerstag, 19. Juni 2014, 08:11:21 schrieb tdjames:
> I'm relatively new to Linux and working on getting a real-time kernel up and
> running for robot applications. I'm on Ubuntu 14.04, using kernel 3.14.3
> and the 3.14.3-rt5 real-time patch. Also using x86-64.

I don?t know about lazy preempt, but maybe a search in make nconfig reveals
more?

In any case: Debian offers ready made rt kernels as packages. So maybe thats an
option for you? Beware: Debian and Ubuntu kernel packaging is different. Maybe
Ubuntu also has a rt kernel package?

Ciao,
--
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7

2014-06-19 15:36:06

by Heinz Diehl

Subject: Re: How to disable Lazy Preempt in the kernel

On 19.06.2014, tdjames wrote:

> How do I disable lazy preempt?

echo NO_PREEMPT_LAZY >/sys/kernel/debug/sched_features

2014-06-19 15:49:15

by tdjames

Subject: Re: How to disable Lazy Preempt in the kernel

When I use
echo NO_PREEMPT_LAZY >/sys/kernel/debug/sched_features
(as root), I get the following error:

bash: echo: write error: Invalid argument

How do I get past this? Thanks





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2014-06-19 17:06:03

by Mike Galbraith

Subject: Re: How to disable Lazy Preempt in the kernel

On Thu, 2014-06-19 at 08:49 -0700, tdjames wrote:
> When I use
> echo NO_PREEMPT_LAZY >/sys/kernel/debug/sched_features
> (as root), I get the following error:
>
> bash: echo: write error: Invalid argument
>
> How do I get past this? Thanks

Easy, do.. nothing. (it's build-time disabled on x86_64;)

-Mike