[zeromq-dev] ZeroMQ 4.2 release, planning

[Doron Somech]

No new socket type, I worked at the time on binary message type, might
complete it sometime, but it is not urgent.

If there is a lot of performance penalty we can give it up, I will
find another solution for the Radio-Dish.

What about 96 bytes? same penalty?

Regarding the binding, I'm not sure.

On Sat, Oct 1, 2016 at 9:14 PM, Luca Boccassi <luca.boccassi at gmail.com> wrote:
> On Tue, 2016-09-27 at 09:41 +0300, Doron Somech wrote:
>> Sorry for the late response, increasing the msg_t structure will be
>> great, however this will require changing a lot of binding.
>
> I think I remember we need it for the new socket types, is that correct?
>
> There is a large performance penalty (intuitively due to not fitting
> into a single cache line anymore, but haven't ran perf/cachegrind), and
> the throughput with vsm type messages goes down by 4% (min) and 20%
> (max) for TCP, and 36% (min) 38 (max) for inproc, which is quite a lot,
> so we need to be sure it's worth it.
>
> Regarding the bindings, after a quick search on the Github org, I could
> only see:
>
> https://github.com/zeromq/lzmq/blob/master/src/lua/lzmq/ffi/api.lua#L144
> https://github.com/zeromq/clrzmq4/blob/master/lib/zmq.cs#L28
> https://github.com/zeromq/pyczmq/blob/master/pyczmq/zmq.py#L177
>
> Other bindings just import zmq.h. Did I miss any?
>
>> Sorry for disappearing, baby and full time job is a lot :-), hopefully
>> I'm back...
>
> No worries, perfectly understandable :-)
>
>> On Mon, Aug 29, 2016 at 6:46 PM, Luca Boccassi <luca.boccassi at gmail.com> wrote:
>> > Sorry, I meant if we go with (1), not (2), we might bump the size as
>> > well, since we are already doing another ABI-breaking change.
>> >
>> > I agree on the solution as well.
>> >
>> > On Mon, 2016-08-29 at 17:12 +0200, Pieter Hintjens wrote:
>> >> I'm confused between the (1) and (2) choices, and can't see where
>> >> bumping the message size fits.
>> >>
>> >> Nonetheless, I think bumping the size, fixing the alignment issues,
>> >> and bumping the ABI version is the best solution here.
>> >>
>> >> On Fri, Aug 26, 2016 at 12:33 PM, Luca Boccassi <luca.boccassi at gmail.com> wrote:
>> >> > I've given some more thoughts and testing to the alignment issue. I can
>> >> > reproduce the problem by enabling alignment checks on x86 too.
>> >> >
>> >> > But most importantly, I think we cannot get away from bumping the ABI
>> >> > with this fix, however we rearrange it, simply because applications need
>> >> > to be rebuilt against the new header to be fixed. A simple rebuild of
>> >> > the libzmq.so is not enough. And the way to do this is to bump the ABI
>> >> > so that distros can schedule transitions and rebuilds and so on.
>> >> >
>> >> > So the choice list is now restricted to:
>> >> >
>> >> > 1) Bump ABI
>> >> > 2) Revert the fix and leave everything broken on sparc64 and some
>> >> > aarch64 (rpi3 seems not to be affected, must depend on the SoC flavour)
>> >> >
>> >> > If we go with 2, we might as well get 2 birds with one stone and bump
>> >> > the zmq_msg_t size to 128 as we have talked about in the past.
>> >> >
>> >> > Doron, this would help with the new UDP based socket types right?
>> >> >
>> >> > Pros of bumping msg size:
>> >> >
>> >> > - we can get rid of the malloc() in the lmsg type case as all the data
>> >> > will fit
>> >> >
>> >> > Cons:
>> >> >
>> >> > - for the vsm/cmsg type cases (for most architectures anyway) it won't
>> >> > fit anymore into a single cacheline
>> >> >
>> >> > Given all this, I'd say we should go for it.
>> >> >
>> >> > Opinions?
>> >> >
>> >> > On Sat, 2016-08-13 at 16:59 +0100, Luca Boccassi wrote:
>> >> >> Hello,
>> >> >>
>> >> >> Trying to give some thoughts again on the libzmq 4.2 release. It's
>> >> >> really long overdue!
>> >> >>
>> >> >> The main issue from my point of view is this change:
>> >> >>
>> >> >> https://github.com/zeromq/libzmq/commit/d9fb1d36ff2008966af538f722a1f4ab158dbf64
>> >> >>
>> >> >> -typedef struct zmq_msg_t {unsigned char _ [64];} zmq_msg_t;
>> >> >>  +/* union here ensures correct alignment on architectures that require
>> >> >> it, e.g.
>> >> >>  + * SPARC
>> >> >>  + */
>> >> >>  +typedef union zmq_msg_t {unsigned char _ [64]; void *p; } zmq_msg_t;
>> >> >>
>> >> >>
>> >> >> This is flagged by the common ABI checkers tools as an ABI breakage
>> >> >> (see: http://abi-laboratory.pro/tracker/timeline/zeromq/ ). And it makes
>> >> >> sense from this point of view: if some applications on some
>> >> >> architectures are broken due to wrong alignment, they would need to be
>> >> >> rebuilt, and the way to ensure that is to bump the ABI "current" digit
>> >> >> to make sure maintainers do a rebuild.
>> >> >>
>> >> >> On the other hand, signaling an ABI breakage is a pain, and a cause of
>> >> >> major churn for packagers and maintainers. It means for example a new
>> >> >> package has to be created (eg: libzmq5 -> libzmq6), and a transition has
>> >> >> to be started and all reverse dependencies need to be rebuilt. And if
>> >> >> this is pointless for all save a few corner cases (eg SPARC64 as for
>> >> >> above) it's all quite frustrating.
>> >> >>
>> >> >> So we have a choice to make before we release 4.2, four possibilities as
>> >> >> far as I can see:
>> >> >>
>> >> >> 1) Ignore the ABI checkers and get yelled at by maintainers and
>> >> >> packagers. Also the SPARC64 users will most likely NOT get their bug
>> >> >> fixed
>> >> >> 2) Bump ABI revision to 6 and get yelled at by maintainers and packagers
>> >> >> 3) Revert the above change and postpone it to when we have a more
>> >> >> generally useful reason to break ABI (bump zmq_msg_t from 64 to 128
>> >> >> bytes for example, Doron?)
>> >> >> 4) Try to be clever and revert the above change and use something like
>> >> >> #pragma pack(8). This will fool the ABI checkers (I tried it), and given
>> >> >> that typedef is only used externally to allocate the right size it
>> >> >> shouldn't actually affect anything, apart from the users of SPARC64
>> >> >> which should get the bugfix with this too. This is very sneaky :-)
>> >> >>
>> >> >> CC'ing Lazslo, the Debian maintainer, given what we choose to do might
>> >> >> result in a lot of work for him :-)
>> >> >>
>> >> >> Opinions?
>> >> >>
>> >> >> Kind regards,
>> >> >> Luca Boccassi
>> >> >>
>> >> >> On Tue, 2016-05-03 at 10:39 +0200, Pieter Hintjens wrote:
>> >> >> > Hi all,
>> >> >> >
>> >> >> > I'm just throwing some ideas on the table. We have a good package of
>> >> >> > work on master and it's probably time to make a 4.2 release.
>> >> >> >
>> >> >> > Luca has already back-ported the enable/disable draft design from
>> >> >> > zproject (CZMQ et al). Yay! So we can now release stable master
>> >> >> > safely, while continuing to refine and extend the draft API sections.
>> >> >> >
>> >> >> > I propose:
>> >> >> >
>> >> >> > - to end with the stable fork policy; this was needed years ago when
>> >> >> > we had massively unstable masters. It's no longer a problem.
>> >> >> > - to use the github release function for libzmq releases and deprecate
>> >> >> > the separate delivery of tarballs.
>> >> >> > - we aim to make a 4.2.0 rc asap, then fix any issues we get, with
>> >> >> > patch releases as usual.
>> >> >> > - we backport the release function to older maintained releases (4.1,
>> >> >> > 3.2) so that their tarballs are provided by github instead of
>> >> >> > downloads.zeromq.org.
>> >> >> >
>> >> >> > Problems:
>> >> >> >
>> >> >> > - this will break a few things that depend on downloads.zeromq.org. To
>> >> >> > be fixed as we go.
>> >> >> > - github tarballs are not identical to source tarballs, particularly
>> >> >> > they lack `configure`. I propose changing our autotools build
>> >> >> > instructions so they always start with `./autogen,sh` no matter where
>> >> >> > the sources come from.
>> >> >> >
>> >> >> > I think this will work and also let us gracefully deprecate/switch off
>> >> >> > the downloads box.
>> >> >> >
>> >> >> > -Pieter
>> >> >> > _______________________________________________
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>> >> >> > zeromq-dev at lists.zeromq.org
>> >> >> > http://lists.zeromq.org/mailman/listinfo/zeromq-dev
>> >> >>
>> >> >>
>> >> >
>> >> >
>> >> >
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