On 03/09/2018 03:01 PM, Rao Shoaib wrote:

On 03/09/2018 02:19 PM, Mat Martineau wrote:

Hi Rao -

On Thu, 22 Feb 2018, Rao Shoaib wrote:

Hi Folks,

When we met with David Miller and Eric Dumazet about a year ago to discuss how to include MPTCP in the main Linux distribution, they wanted to have some code that could be evaluated and used at the basis for discussion.

The patches that I have submitted are for starting that discussion only and nothing else. If the approach is acceptable we can do more cleanup, If not we will have a discussion and hopefully agree on something.

I would like to send the patches, perhaps a week from now to the netdev mailing list to start a discussion there and come up with a plan to implement MPTCP.

Comments/Suggestions ?

I saw that you posted some questions on netdev this week and got some maintainer feedback: https://marc.info/?t=152039384300002&r=1&w=2

David mentions:

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.

Yes against all objections I did post to net-dev and got some very informative answers. David is not allowing indirect function calls because of the security issues. You should see the comments that Linus has made about the fixes and folks asking for an alternative as they are heavily used.

Sorry wrong url -- See


Edit: To give a bit more background, predicting indirect calls and speculating into them is absolutely critical to getting good performance from OOP-ish code which tends to use them a lot (virtual functions in C++, function pointers in C). The Linux kernel is (thankfully?) not very OOP-ish, but it does rely on indirect calls (function pointers) extensively.


It's not immediately clear which techniques are being looked at (and both Eric and David did not elaborate when you followed up). I'm trying to find out which alternatives he's referring to - anyone else seen information on this?
Nope. It's not clear what the solution will be, but that should not have any impact on the patch that we submitted. As a simple fix we can add if/else as there are only two ways to go.

Please see my email and comment.



Mat Martineau
Intel OTC

mptcp mailing list