linux-kernel - Re: [PATCH v2 0/4] Static calls

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Date:   Wed, 12 Dec 2018 17:11:00 +0000
From:   Edward Cree <ecree@...arflare.com>
To:     Nadav Amit <namit@...are.com>, Josh Poimboeuf <jpoimboe@...hat.com>
CC:     LKML <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH v2 0/4] Static calls

On 12/12/18 05:59, Nadav Amit wrote:
> Thanks for cc’ing me. (I didn’t know about the other patch-sets.)
Well in my case, that's because I haven't posted any yet.  (Will follow up
 shortly with what I currently have, though it's not pretty.)

Looking at your patches, it seems you've got a much more developed learning
 mechanism.  Mine on the other hand is brutally simple but runs continuously
 (i.e. after we patch we immediately enter the next 'relearning' phase);
 since it never does anything but prod a handful of percpu variables, this
 shouldn't be too costly.

Also, you've got the macrology for making all indirect calls use this,
 whereas at present I just have an open-coded instance on a single call site
 (I went with deliver_skb in the networking stack).

So I think where we probably want to go from here is:
 1) get Josh's static_calls in.  AIUI Linus seems to prefer the out-of-line
    approach; I'd say ditch the inline version (at least for now).
 2) build a relpolines patch series that uses
   i) static_calls for the text-patching part
  ii) as much of Nadav's macrology as is applicable
 iii) either my or Nadav's learning mechanism; we can experiment with both,
      bikeshed it incessantly etc.

Seem reasonable?

-Ed