linux-kernel - Re: [PATCH v2] arm64: Disable branch profiling for all arm64 code

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Message-ID: <frfmxk2ifpf5shcws42q3eeykb3xyflxocbic6junm7mzvmqik@vktwefe2zmw7>
Date: Wed, 7 Jan 2026 01:37:36 -0800
From: Breno Leitao <leitao@...ian.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Mark Rutland <mark.rutland@....com>, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Laura Abbott <labbott@...hat.com>, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	Masami Hiramatsu <mhiramat@...nel.org>, kernel-team@...a.com, puranjay@...nel.org, 
	stable@...r.kernel.org
Subject: Re: [PATCH v2] arm64: Disable branch profiling for all arm64 code

Hello Steven,

On Tue, Jan 06, 2026 at 11:11:42AM -0500, Steven Rostedt wrote:
> On Tue, 6 Jan 2026 12:24:09 +0000
> Mark Rutland <mark.rutland@....com> wrote:
> 
> 
> > Whoops; s/CONFIG_DEBUG_VIRTUAL/PROFILE_ANNOTATED_BRANCHES/ in both
> > places in my reply.
> 
> Note, it could still be useful ;-) 
> 
> I've been running my yearly branch profiling build on both my main
> workstation and my server. I post the results from my server publicly (this
> is updated every night):
> 
>    https://rostedt.org/branches/current
> 
> If you check out the branch_annotated file, you can see there's still quite
> a bit that gets it wrong. Some of these is because of bad assumptions by
> the developer, others is because the code moved around causing new branches
> to make later annotated branches go the opposite way.

I am starting to look and remove some of these likely/unlikely hint that
are 100% wrong on some very sane configuration (arm64 baremetal hosts
running a webserver).

So far, these are the fixes I have in flight now.

 * https://lore.kernel.org/all/20260105-dcache-v1-1-f0d904b4a7c2@debian.org/
 * https://lore.kernel.org/all/20260106-blk_unlikely-v1-1-90fb556a6776@debian.org/
 * https://lore.kernel.org/all/20260105-annotated_idle-v1-1-10ddf0771b58@debian.org/