sbanach

With Java vs C++, the experience seems similar. In C++, memory allocation is slow, so you worry about memory allocation up front. In Java, GC is a pain so you worry about memory allocation up front. As Daniel points out, there are a few extra tricks available to native developers (eg vector instructions), so there's a small factor speed-up in best-practice C++ vs best-practice Java, but this is closing (eg the JIT increasingly uses vector instructions). Overwhelmingly the difference between a slow system and a fast system is appropriate choices of algorithms and architecture, not the language.

The compression format is really smart, there's a neat trick to make the logarithm calculation fast, and there's a concurrent thread handoff mechanism so you can swap out a histogram without disturbing the thread you're measuring (though last two probably only in the java version). Those three make it super useful for very low impact performance measurements.

Google claims 3.5 billion queries per day, so approaching 1% of that.

Congratulations!

High frequency trading?

That's pretty interesting. Is there a concrete example of a quorum definition where the probability of an outlier is improved vs majority quorum? I'm struggling to come up with one. I've always assumed majority is optimal, since you can tolerate outliers in (n-1) / 2 voters without seeing an outlier for the commit overall. Eg: for 3 node Raft - you'd need both followers to have an outlier before a client notices a slow commit.

On hotspot: There are two bits in the header of every object. This is enough for an object that's never been used as a contended lock, CAS operations on the header can be used to handle the locking and that's that. As soon as you actually block on it, a 'real' lock is created (you can't get around the need for a list of threads to wake up as the lock is released) and the header grows to accomodate it. The process is called 'monitor inflation'. At a later date this might be cleaned up by a 'monitor deflation'.

Quick question: What's the draw of using Netty vs pure java.nio? The latter (Selectors, Socket/DatagramChannels, ByteBuffers etc) seems reasonably straightforward to use, so I've never really looked at a framework - am I missing out?

The distinction arises when the full text of a clause is not possible to claim by law, but some weakened or lesser version is OK: If you missed the 'maximum extent permissible' part, your clause would be completely invalidated. Its a hedge.

Yes, given the solarflare I was expecting the article to end up with a receiver coded against ef_vi, which exposes the NIC memory directly (but you have to do the IP/UDP yourself)

So arm compilers must prefer to, for example, XOR with 0x10000000 rather than AND with 0xEFFFFFFF?