Re: [dpdk-dev] [PATCH 0/8] eBPF arm64 JIT support

[Jerin Jacob <jerinjacobk@gmail.com>]

On Thu, Oct 3, 2019 at 8:35 PM Ananyev, Konstantin
<konstantin.ananyev@intel.com> wrote:
>
> Hi everyone,
>
> >
> > On Thu, Oct 3, 2019 at 6:21 PM Thomas Monjalon <thomas@monjalon.net> wrote:
> > >
> > > 03/09/2019 12:59, jerinj@marvell.com:
> > > > Added eBPF arm64 JIT support to improve the eBPF program performance
> > > > on arm64.
> > > >
> > > >  lib/librte_bpf/bpf_jit_arm64.c         | 1451 ++++++++++++++++++++++++
> > >
> > > I am concerned about duplicating the BPF JIT effort in DPDK and Linux.
> > > Could we try to pull the Linux JIT?
> > > Is the license the only issue?
> >
> > That's one issue.
> >
> > >
> > > After a quick discussion, it seems the Linux authors are OK to arrange
> > > their JIT code for sharing with userspace projects.
> >
> > I did a clean room implementation considering some optimization for
> > DPDK etc(Like if stack is not used then don't push stack etc)
> > and wherever Linux can be improved, I have submitted the patch also to
> > Linux as well.(Some more pending as well)
> >
> > https://github.com/torvalds/linux/commit/504792e07a44844f24e9d79913e4a2f8373cd332
> >
> > And Linux has a framework for instruction generation for debugging
> > etc. So We can not copy and paste the code
> > from Linux as is.
> >
> > My view to keep a different code base optimize for DPDK use cases and
> > library requirements(for example, tail call is not supported in DPDK).
> > For arm64/x86 case the code is done so it is not worth sync with
> > Linux. For new architecture, it can be if possible.
> >
> > Konstantin,
> > Your thoughts?
> >
>
> My thought would be that if we have JIT eBPF compiler already in DPDK
> for one arch (x86) there is absolutely no reason why we shouldn't allow it for different arch (arm).
> About having a common code-base with Linux eBPF JITs implementation -
> I think it is a very good idea,
> but I don’t' think it could be achieved without significant effort.
> DPDK and Linux JIT code-generators differ quite a bit.
> So my suggestion - let's go ahead and integrate Jerin patch into 19.11,
> meanwhile start talking with linux guys how common JIT code-base could be achieved.

I agree with Konstantin here.

Thomas,

Just confirm the following:

While we continue to have 'advanced' discussion on avoiding code duplication etc
and it will take a couple of months to converge(if at all it happens)

Just to be clear, I assume, you are OK to merge this code for 19.11(If
no more technical comment on the patch).

I am only afraid of, our typical last-minute surprise pattern and
followed by back and forth open ended discussions.

i.e

# Code submitted before the proposal window
# Gets ACK from Maintainer
# New non-technical concerns start just before RC1










> Konstantin
>
>
>
>