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

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Message-ID: <Y87HxUN/mcC99Xj6@FVFF77S0Q05N>
Date:   Mon, 23 Jan 2023 17:45:41 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Steven Rostedt <rostedt@...dmis.org>
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, Jan 23, 2023 at 12:11:47PM -0500, Steven Rostedt wrote:
> 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." 

Sounds good to me! :)

FWIW, with that:

Acked-by: Mark Rutland <mark.rutland@....com>

> > 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.

Thanks!

> > 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.

Fair enough!

Mark.