Back to the Future with C++ and Seastar

[Erez D]

On Thu, Apr 2, 2015 at 12:14 AM, Amos Shapira <amos.shapira at gmail.com>
wrote:

> Hi Nadav,
>
> Will it be video taped?
> Slides made available?
>
That would be great

>
> Thanks,
>
> --Amos
>
> On 2 April 2015 at 05:53, Nadav Har'El <nyh at math.technion.ac.il> wrote:
>
>> On Wed, Apr 01, 2015, Oleg Goldshmidt wrote about "Re: Back to the Future
>> with C++ and Seastar":
>> > "Nadav Har'El" <nyh at math.technion.ac.il> writes:
>> > > Seastar is an open source (http://www.seastar-project.org/) library.
>> > > It is based on the concept of "futures" (like in Node.js, just
>> implemented
>> > > in a much more efficient way). Part of the talk will also introduce
>> futures,
>> > > how Seastar implements them in C++, and how much C++ has changed in
>> recent
>> > > years from what you may remember about it.
>> >
>> > I might come (close to work :). C++ has futures and promises natively,
>> > as a part of its standard library. Can you add a couple of words on how
>> > Seastar's futures differ?
>>
>> Sure, though I'm sure Avi will explain it better in his talk :-)
>>
>> The first difference is that C++11's support for futures is incomplete:
>> Futures are supported, but not *continuations*, which are code you want
>> to run when the future value becomes available. C++17 will probably have
>> continuations, but Seastar has them now.
>>
>> The second difference is that C++11's futures are indeed powerful, but not
>> optimized for performance. They make excessive use of allocations, they
>> rely on threads and everything uses atomic operations and locks. Seastar's
>> design, on the other hand, is aimed at modern SMP design, for achieving
>> the top possible performance: Continuations are very lightweight (not
>> based on thread context switching), you write with Seastar a share-nothing
>> server (each core deals with its own data) so no locks, no atomic
>> operations,
>> and very little cache contention. These things make a *huge* difference
>> in performance in modern SMPs - especially when you try to scale up to
>> many cores.
>>
>> The third difference is that Seastar is much more than just an
>> implementation of futures - it is a complete library for writing
>> asynchronous I/O-heavy (network and disk) applications - consider http
>> servers, proxies, nosql servers - any server application you can think of
>> will be much faster if rewritten in Seastar (Avi will present some
>> benchmarks, showing near perfect scalability to 40 cores, 5x speed
>> improvements compared to traditional thought-to-be-efficient applications,
>> etc. Seastar completely bypasses the operating system by using DPDK,
>> but as you may know DPDK only supports L2 packets and has no TCP/IP stack.
>> But that's no longer true: We actually implemented in Seastar a full
>> TCP/IP stack over DPDK, write in Seastar's own futures framework.
>>
>> And Seastar is even more. I'll leave a few surprises for Avi's talk ;-)
>>
>> --
>> Nadav Har'El                        |     Wednesday, Apr 1 2015, 13 Nisan
>> 5775
>> nyh at math.technion.ac.il
>>  |-----------------------------------------
>> Phone +972-523-790466, ICQ 13349191 |My opinions may have changed, but
>> not the
>> http://nadav.harel.org.il           |fact that I am right.
>>
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>
>
>
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> <http://au.linkedin.com/in/gliderflyer>
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