linux-kernel - Re: [PATCH RFC 1/2] m68k: Add tracirqs

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Message-ID: <ec30a0d3-6d53-4350-a26b-c4d8b41057ec@yoseli.org>
Date: Wed, 23 Oct 2024 11:31:40 +0200
From: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Steven Rostedt <rostedt@...dmis.org>, linux-m68k@...ts.linux-m68k.org,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 1/2] m68k: Add tracirqs

Hi Geert,

On 23/10/2024 11:13, Geert Uytterhoeven wrote:
> Hi Jean-Michel,
> 
> On Wed, Oct 23, 2024 at 11:07 AM Jean-Michel Hautbois
> <jeanmichel.hautbois@...eli.org> wrote:
>> On 23/10/2024 10:47, Steven Rostedt wrote:
>>> On Tue, 22 Oct 2024 11:21:34 +0200
>>> Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org> wrote:
>>>> I was not really expecting you to review the m68k one no :-).
>>>> I think I have other issues which might have impact on ftrace too.
>>>> For instance, when I launch cyclictest I have a warning about HRTIMERS:
>>>> # cyclictest -p 99
>>>> WARN: stat /dev/cpu_dma_latency failed: No such file or directory
>>>> WARN: High resolution timers not available
>>>> policy: fifo: loadavg: 1.21 0.40 0.14 1/122 245
>>>>
>>>> T: 0 (  245) P:99 I:1000 C:  11203 Min:     92 Act:  623 Avg:  775 Max:
>>>>      3516
>>>>
>>>> The latencies are quite high...
>>>
>>> Yes, if you don't have high resolution timers, the latency will be high.
>>
>> According to my config, I should have those:
>> CONFIG_HIGH_RES_TIMERS=y
> 
> Does your hardware have a high resolution timer, and do you have
> a driver for it?
> 
> $ git grep hrtimer -- arch/m68k/
> $
>

No, there is nothing with hrtimer. But, the architecture has four dma 
timers, with a 8ns resolution at 125MHz says the documentation. I will 
try to find a way to implement the missing part.

Thanks,
JM

> Gr{oetje,eeting}s,
> 
>                          Geert
>