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Date: Thu, 21 Mar 2024 10:49:39 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: "Bj\"orn T\"opel" <bjorn@kernel.org>, Puranjay Mohan
 <puranjay12@gmail.com>, Paul Walmsley <paul.walmsley@sifive.com>, Palmer
 Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, Masami
 Hiramatsu <mhiramat@kernel.org>, Sami Tolvanen <samitolvanen@google.com>,
 Guo Ren <guoren@kernel.org>, Ley Foon Tan <leyfoon.tan@starfivetech.com>,
 Deepak Gupta <debug@rivosinc.com>, Sia Jee Heng
 <jeeheng.sia@starfivetech.com>, "Bj\"orn T\"opel" <bjorn@rivosinc.com>,
 Song Shuai <suagrfillet@gmail.com>, Cl'ement L'eger <cleger@rivosinc.com>,
 Al Viro <viro@zeniv.linux.org.uk>, Jisheng Zhang <jszhang@kernel.org>,
 linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
 linux-trace-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] riscv: Implement HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS
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On Tue, 12 Mar 2024 13:42:28 +0000
Mark Rutland <mark.rutland@arm.com> wrote:

> > It would be interesting to see how the per-call performance would
> > improve on x86 with CALL_OPS! ;-)  
> 
> Heh. ;)

But this would require adding -fpatchable-function-entry on x86, which
would increase the size of text, which could possibly have a performance
regression when tracing is disabled.

I'd have no problem if someone were to implement it, but there's a strict
requirement that it does not slow down the system when tracing is disabled.
As tracing is a second class citizen compared to the rest of the kernel.

-- Steve