linux-kernel - Re: [PATCH 1/2] x86: Remove dynamic NOP selection

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Message-ID: <020a1803-25c4-4365-8c53-291becd94632@zytor.com>
Date: Sun, 21 Jan 2024 18:15:39 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Thorsten Glaser <tg@...ian.org>, Peter Zijlstra <peterz@...radead.org>,
        x86@...nel.org, torvalds@...uxfoundation.org,
        linux-kernel@...r.kernel.org, linux-toolchains@...r.kernel.org,
        jpoimboe@...hat.com, alexei.starovoitov@...il.com, mhiramat@...nel.org
Subject: Re: [PATCH 1/2] x86: Remove dynamic NOP selection

On 1/21/24 16:56, Steven Rostedt wrote:
>>
>> Yes, but it is a matter of where we optimize for performance as opposed to correctness.
> 
> There is no such thing as "optimize for correctness", it is either
> correct or it is not. Correctness should always come before performance
> (at least that is what Thomas has pounded into me ;-)
> 
> If a kernel use to work on a machine but a newer version no longer
> works, I call that a regression.
> 

There absolutely is such a thing as "optimize for correctness." It means 
to keep the code clean, easily testable, and with a minimal number of 
distinct code paths so that regressions and *especially* uncaught 
regressions get caught quickly.

	-hpa