linux-kernel - Re: [PATCH] ftrace/scripts: Update the instructions for ftrace-bisect.sh

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Date:   Mon, 23 Jan 2023 12:11:47 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH] ftrace/scripts: Update the instructions for
 ftrace-bisect.sh

On Mon, 23 Jan 2023 16:59:55 +0000
Mark Rutland <mark.rutland@....com> wrote:

> > +# The old (slow) way, for kernels before v5.1.
> > +#
> > +# [old-way] # cat available_filter_functions > ~/full-file
> > +#
> > +# [old-way] *** Note *** this will take several minutes. Setting multiple
> > +# [old-way] functions is an O(n^2) operation, and we are dealing with thousands
> > +# [old-way] of functions. So go have  coffee, talk with your coworkers, read
> > +# [old-way] facebook. And eventually, this operation will end.  
> 
> Super-trivial nit, but the above step isn't actually that expensive, and it's
> the subsequent write to set_ftrace_filter that's going to be slow.

How about:

 "*** Note *** this process will take several minutes to update the filters." 


> 
> That double spacing in 'go have  coffee' looks odd; is that an old error from
> reformatting a line break, and/or a missing 'a' ?

I can fix that.

> 
> How about:
> 
> # [old-way] *** Note *** writing function names to set_ftrace_filter will take
> # [old-way] several minutes. Setting multiple functions is an O(n^2) operation,
> # [old-way] and we will set thousands of functions. So for subsequent steps,
> # [old-way] go have a coffee, talk with your coworkers, read facebook. And
> # [old-way] eventually, this operation will end.
> 
> ... or leave this in place below, and add "If using [old-way] ..." to the start?

I wanted to explicitly show that the above is only a reference to the old
way, and leave no doubt about it. It was either doing this or deleting it
completely. I chose to keep it.

> 
> Regardless, this looks sensible to me!

Thanks, I'll send a v2 with the nit updates.

-- Steve