IMX53 on recent 4.4.x kernels

[Vellemans, Noel]

Hi all, 

As soon as I read the hints from Russell,  I was convinced that there COULD be a big performance gain , by disabling debugging features.

I did not find time to check this ( we have national holidays here in our country, and we start our annual holidays)

But you can count on it when I test  (russell's hint's)  I'll report back my findings, but .. i'm almost sure , and  it is at least pointing me into a direction to look at, one that I overlooked..)

I see that Fabio did test, russell's hint's and that he had a huge improvement, fabio's first test results look promising , thats for sure ! 

Like Russel says, and like we all understand, it's a balance of functions vs performance. 

Thanks all for the Hints.. and I'll report back as soon as possible.

Keeping fingers crossed in the meantime. 

Regards 
Noel




________________________________________
From: Russell King - ARM Linux [linux at armlinux.org.uk]
Sent: Friday, July 21, 2017 6:34 PM
To: Fabio Estevam
Cc: Vellemans, Noel; Pengutronix Sales Team; Robert Schwebel; linux-arm-kernel at lists.infradead.org
Subject: Re: IMX53 on recent 4.4.x kernels

On Fri, Jul 21, 2017 at 01:29:08PM -0300, Fabio Estevam wrote:
> Hi Russell,
>
> On Thu, Jul 20, 2017 at 8:53 PM, Russell King - ARM Linux
> <linux at armlinux.org.uk> wrote:
>
> > Another thing to check is that you have features like the spinlock
> > debug, semaphore debug, lockdep, tracing etc all disabled - these
> > can add quite a bit of additional processing into critical paths.
>
> Yes, this really helps.
>
> On my tests with Noel's application the execution time goes from 41 to
> 22 seconds on kernel 4.13-rc1.
>
> Here is the defconfig changes generated by manually removing these
> features and then using savedefconfig:

Note - you want lockdep and so forth enabled for development kernels
to catch bugs before changes are submitted upstream.  However, for
kernels that you care about performance, you need to have them disabled.

Like everything it's a balance between function and performance.

--
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