On Wed, Apr 01, 2015, Oleg Goldshmidt wrote about "Re: Back to the Future with C++ and Seastar": > "Nadav Har'El" <n...@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 n...@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. _______________________________________________ Linux-il mailing list Linux-il@cs.huji.ac.il http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
