The problem is that spectulative execution is fundamental to performance in systems that have conditionals. With memory latencies being ~100ns, and a 3GHz core

The problem is that spectulative execution is fundamental to performance in systems that have conditionals. With memory latencies being ~100ns, and a 3GHz core, you waste 300 cycles every time you need to load the conditional from RAM, and maybe 50 cycles if you need to load it from L3 cache. Branch prediction is generally pretty accurate, so avoiding that penalty is crucial if you want to go fast. Now, maybe it is possible to reduce use of indirect branches . C++ for example, is pretty gratuitous in that respect. But in the end, most software is going to perform a lot slower without speculative execution. I don't think that's a price worth paying. What will happen is the CPU vendors will fix meltdown (which should never have happened) and Spectre 2. Sharing the branch history buffer between contexts is something that fundamentally can be avoided, in the same way we can tag TLB entries with the PCID on recent hardware. In the long run, the real issue is Spectre 1. Using software to contain untrusted software in the same address space is fundamentally hard with speculative execution. After all the fuss has died down, that's where we'll see innovative software techniques. It's already starting to happen, if you look at the webkit changes (scroll down to Branchless Security Checks): https://webkit.org/blog/8048/what-spectre-and-meltdown-mean-for-webkit/ https://webkit.org/blog/8048/what-spectre-and-meltdown-mean-...