netdev - Re: [net-next 01/12] i40e: replace switch-statement to speed-up retpoline-enabled builds

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Message-ID: <806f5242-d509-e015-275e-ad0325f17222@iogearbox.net>
Date:   Thu, 2 May 2019 16:47:37 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>, davem@...emloft.net
Cc:     Björn Töpel <bjorn.topel@...el.com>,
        netdev@...r.kernel.org, nhorman@...hat.com, sassmann@...hat.com,
        Andrew Bowers <andrewx.bowers@...el.com>
Subject: Re: [net-next 01/12] i40e: replace switch-statement to speed-up
 retpoline-enabled builds

On 04/29/2019 09:16 PM, Jeff Kirsher wrote:
> From: Björn Töpel <bjorn.topel@...el.com>
> 
> GCC will generate jump tables for switch-statements with more than 5
> case statements. An entry into the jump table is an indirect call,
> which means that for CONFIG_RETPOLINE builds, this is rather
> expensive.
> 
> This commit replaces the switch-statement that acts on the XDP program
> result with an if-clause.
> 
> The if-clause was also refactored into a common function that can be
> used by AF_XDP zero-copy and non-zero-copy code.

Isn't it fixed upstream by now already (also in gcc)?

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ce02ef06fcf7a399a6276adb83f37373d10cbbe1
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a9d57ef15cbe327fe54416dd194ee0ea66ae53a4