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Message-ID: <0c73af48-d638-dd58-fcf8-c872ff8591d7@intel.com>
Date:   Thu, 2 May 2019 22:29:45 +0200
From:   Björn Töpel <bjorn.topel@...el.com>
To:     Daniel Borkmann <daniel@...earbox.net>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>, davem@...emloft.net
Cc:     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 2019-05-02 16:47, Daniel Borkmann wrote:
> 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
> 

Hmm, given that Daniel's work is upstream, this patch doesn't really
make sense any more. OTOH it can stay in the series, and be cleaned up
later.

I'll leave it for you to decide, Jeff!


Cheers,
Björn

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