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From Stephan Ewen <se...@apache.org>
Subject Re: Tuple performance and the curious JIT compiler
Date Wed, 09 Mar 2016 13:49:15 GMT
Do we have consensus that we want to "reserve" this topic for a GSoC
student?

It is becoming a feature that gains more importance. To see we can "hold
off" on working on that, would be good to know a bit more, like
  - when is it decided whether this project takes place?
  - when would results be there?
  - can we expect the results to be usable, i.e., how good is the student?
(no offence, but so far the results in GSoC were everywhere between very
good and super bad)

Greetings,
Stephan


On Tue, Mar 8, 2016 at 4:28 PM, Márton Balassi <balassi.marton@gmail.com>
wrote:

> @Fabian: That is my bad, but I think we should be still on time. Pinged Uli
> just to make sure. Proposal from Gabor and Jira from me are coming soon.
>
> On Tue, Mar 8, 2016 at 11:43 AM, Fabian Hueske <fhueske@gmail.com> wrote:
>
> > Hi Gabor,
> >
> > I did not find any Flink proposals for this year's GSoC in JIRA (should
> be
> > labeled with gsoc2016).
> > I am also not sure if any of the Flink committers signed up as a GSoC
> > mentor.
> > Maybe it is still time to do that but as it looks right now there are no
> > GSoC projects offered by Flink.
> >
> > Best, Fabian
> >
> >
> >
> >
> >
> >
> > 2016-03-08 11:22 GMT+01:00 Gábor Horváth <xazax.hun@gmail.com>:
> >
> > > Hi!
> > >
> > > I am planning to do GSoC and I would like to work on the serializers.
> > More
> > > specifically I would like to implement code generation. I am planning
> to
> > > send the first draft of the proposal to the mailing list early next
> week.
> > > If everything is going well, that will include some preliminary
> > benchmarks
> > > how much performance gain can be expected from hand written
> serializers.
> > >
> > > Best regards,
> > > Gábor
> > >
> > > On 8 March 2016 at 10:47, Stephan Ewen <sewen@apache.org> wrote:
> > >
> > > > Ah, very good, that makes sense!
> > > >
> > > > I would guess that this performance difference could probably be seen
> > at
> > > > various points where generic serializers and comparators are used
> (also
> > > for
> > > > Comparable, Writable) or
> > > > where the TupleSerializer delegates to a sequence of other
> > > TypeSerializers.
> > > >
> > > > I guess creating more specialized serializers would solve some of
> these
> > > > problems, like in your IntValue vs LongValue case.
> > > >
> > > > The best way to solve that would probably be through code generation
> in
> > > the
> > > > serializers. That has actually been my wish for quite a while.
> > > > If you are also into these kinds of low-level performance topics, we
> > > could
> > > > start a discussion on that.
> > > >
> > > > Greetings,
> > > > Stephan
> > > >
> > > >
> > > > On Mon, Mar 7, 2016 at 11:25 PM, Greg Hogan <code@greghogan.com>
> > wrote:
> > > >
> > > > > The issue is not with the Tuple hierarchy (running Gelly examples
> had
> > > no
> > > > > effect on runtime, and as you note there aren't any subclass
> > overrides)
> > > > but
> > > > > with CopyableValue. I had been using IntValue exclusively but had
> > > > switched
> > > > > to using LongValue for graph generation. CopyableValueComparator
> and
> > > > > CopyableValueSerializer are now working with multiple types.
> > > > >
> > > > > If I create IntValue- and LongValue-specific versions of
> > > > > CopyableValueComparator and CopyableValueSerializer and modify
> > > > > ValueTypeInfo to return these then I see the expected performance.
> > > > >
> > > > > Greg
> > > > >
> > > > > On Mon, Mar 7, 2016 at 5:18 AM, Stephan Ewen <sewen@apache.org>
> > wrote:
> > > > >
> > > > > > Hi Greg!
> > > > > >
> > > > > > Sounds very interesting.
> > > > > >
> > > > > > Do you have a hunch what "virtual" Tuple methods are being used
> > that
> > > > > become
> > > > > > less jit-able? In many cases, tuples use only field accesses
> (like
> > > > > > "vakle.f1") in the user functions.
> > > > > >
> > > > > > I have to dig into the serializers, to see if they could suffer
> > from
> > > > > that.
> > > > > > The "getField(pos)" method for example should always have many
> > > > overrides
> > > > > > (though few would be loaded at any time, because one usually
does
> > not
> > > > use
> > > > > > all Tuple classes at the same time).
> > > > > >
> > > > > > Greetings,
> > > > > > Stephan
> > > > > >
> > > > > >
> > > > > > On Fri, Mar 4, 2016 at 11:37 PM, Greg Hogan <code@greghogan.com>
> > > > wrote:
> > > > > >
> > > > > > > I am noticing what looks like the same drop-off in performance
> > when
> > > > > > > introducing TupleN subclasses as expressed in "Understanding
> the
> > > JIT
> > > > > and
> > > > > > > tuning the implementation" [1].
> > > > > > >
> > > > > > > I start my single-node cluster, run an algorithm which
relies
> > > purely
> > > > on
> > > > > > > Tuples, and measure the runtime. I execute a separate jar
which
> > > > > executes
> > > > > > > essentially the same algorithm but using Gelly's Edge (which
> > > > subclasses
> > > > > > > Tuple3 but does not add any extra fields) and now both
the
> Tuple
> > > and
> > > > > Edge
> > > > > > > algorithms take twice as long.
> > > > > > >
> > > > > > > Has this been previously discussed? If not I can work up
a
> > > > > demonstration.
> > > > > > >
> > > > > > > [1]
> > https://flink.apache.org/news/2015/09/16/off-heap-memory.html
> > > > > > >
> > > > > > > Greg
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

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