linux-kernel - Re: [PATCH] x86/fred: Optimize the FRED entry by prioritizing high-probability event dispatching

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Message-ID: <c111ecfe-9055-46f3-8bd0-808a4dc039dd@zytor.com>
Date: Fri, 17 Jan 2025 08:24:43 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Ethan Zhao <haifeng.zhao@...ux.intel.com>, Xin Li <xin@...or.com>,
        Ethan Zhao <etzhao@...look.com>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Cc: tglx@...utronix.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        andrew.cooper3@...rix.com, mingo@...hat.com, bp@...en8.de
Subject: Re: [PATCH] x86/fred: Optimize the FRED entry by prioritizing
 high-probability event dispatching

> 
> In short, seems that __builtin_expect not work with switch(), at least for
>   gcc version 8.5.0 20210514(RHEL).
> 

For forward-facing optimizations, please don't use an ancient version of 
gcc as the benchmark.

	-hpa