linux-kernel - Re: [PATCH 3/3] x86/ftrace: Use text

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Message-ID: <761c5baf-598d-c2da-bd3e-2a669bf16b50@redhat.com>
Date:   Fri, 4 Oct 2019 16:44:35 +0200
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Nadav Amit <nadav.amit@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Song Liu <songliubraving@...com>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH 3/3] x86/ftrace: Use text_poke()

On 04/10/2019 15:40, Steven Rostedt wrote:
> On Fri, 4 Oct 2019 10:10:47 +0200
> Daniel Bristot de Oliveira <bristot@...hat.com> wrote:
> 
>> [ In addition ]
>>
>> Currently, ftrace_rec entries are ordered inside the group of functions, but
>> "groups of function" are not ordered. So, the current int3 handler does a (*):
>>
>> for_each_group_of_functions:
>> 	check if the ip is in the range    ----> n by the number of groups.
>> 		do a bsearch.		   ----> log(n) by the numbers of entry
>> 					         in the group.
>>
>> If, instead, it uses an ordered vector, the complexity would be log(n) by the
>> total number of entries, which is better. So, how bad is the idea of:
> BTW, I'm currently rewriting the grouping of the vectors, in order to
> shrink the size of each dyn_ftrace_rec (as we discussed at Kernel
> Recipes). I can make the groups all sorted in doing so, thus we can
> load the sorted if that's needed, without doing anything special.
> 

Good! if you do they sorted and store the amount of entries in a variable, we
can have things done for a future "optimized" version.

-- Daniel