netdev - Re: Use of Indirect function calls

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Message-ID: <997251f8-b012-b714-a906-653984d56b30@oracle.com>
Date:   Tue, 6 Mar 2018 21:53:19 -0800
From:   Rao Shoaib <rao.shoaib@...cle.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: Use of Indirect function calls

David,

Thanks a lot for your prompt response. Do you have a specific solution 
in mind or will the calls be replaced with simple checks ?

Also while I have your attention can I ask your opinion about breaking 
up some TCP functions, mostly control functions into smaller units so 
that if a little different behavior is desired it can be achieved and 
common code could still be shared. Of course you can not say much 
without looking at the code but will you even entertain such a change ?

Regards,

Rao.

On 03/06/2018 08:43 PM, David Miller wrote:
> From: Rao Shoaib <rao.shoaib@...cle.com>
> Date: Tue, 6 Mar 2018 19:35:46 -0800
>
>> I do not expect any measurable overhead as modern CPU's use
>> pre-fetching and multiple parallel execution engines.
> Please see Spectre and retpolines, all of this parallel execution and
> prefetching is essentially disabled to address those vulnerabilities
> and side-channel exploits.
>
> Indirect calls are terrible and we are now looking at ways in which
> we can remove them from as many parts of the networking as possible.