On 10/24/2013 11:13 AM, Gene Heskett wrote:
> On Thursday 24 October 2013 11:05:25 Kent Reed did opine:
>
>> On Thu, Oct 24, 2013 at 10:10 AM, Gene Heskett <[email protected]> wrote:
>>> <...>
>>>
>>>
>>> Note the isolcpus=1 on the end of the 'linux' line, it has to be hand
>>> edited into that file after the installation is done, and then
>>> rebooted again to enable it.  The UUID's should be different from the
>>> above.
>> It's generally a bad idea to hand-edit the grub.cfg file. It even says
>> why at the top just after the "DO NOT EDIT THIS FILE" comment.
>>
>> I posted a page to the Wiki two years ago  (
>> http://wiki.linuxcnc.org/cgi-bin/wiki.pl?The_Isolcpus_Boot_Parameter_And
>> _GRUB2) about my solution to the problem.
>>
> I think I followed this recipe when I did that.  It does give some extra
> whitespace in front of the argument.
>
> In this case , since we don't normally update the kernel, the grub.cfg
> rebuild isn't being done, so either method would get the job done.

Well, there are other reasons. For instance, one decides to save some 
space by deleting old kernels or one decides to try out an alternative 
kernel, say of the Xenomai or rt_preempt persuasion, on a working 
machine. In either case, update-grub is run to make grub aware of the 
changes.

> What I wanted to offer was a quick & dirty way for the OP to check that it
> was done, just by looking at the generated grub.cfg.
>
>

I hear you , Gene, but the phrase "...it has to be hand edited into that 
file after the installation is done..." is now enshrined in the email 
archives and I didn't want it looking to future readers like a 
recommended practice.

My excessive sense of caution stems from 30 years living with myriad 
systems and applications, many of which bit me in the backside one time 
or another. A quick-n-dirty hack which gets a program going today can 
have a nasty habit of remaining in the code to become a landmine for the 
unsuspecting tomorrow.

I don't claim to be guiltless just because I was often a victim. I've 
left a few landmines of my own.

More to the point, I wish people who feel sufficiently compelled to post 
numbers to the latency-test wiki page would also feel compelled to run 
the tests with these different kernel configurations and post all the 
results. See for example, my three entries for the ASUS AT5NM10-O. This 
would help reduce the amount of handwaving we do on this list.

Just my 2 cents worth.

Regards,
Kent


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