Its characterising memory accesses, so it will show up the result of using all the caches in the system.

You would typically see larger latencies when the caches are not being effective.

Multiple humps will indicate the presence of multi-level caches.

Okay, so how can we deactivate ASM.js and WebAssembly? (in the light of Meltdown and Spectre)

The config in Chrome is broken, WebAssembly cannot be deactivated anymore with chrome://flags/#enable-webassembly , setting it to "deactivated" and it's still active.

Asm.js is not necessary, simple JavaScript interpreter is enough. This demo used to work before most browsers implemented optimizers for Asm.js

Mozilla Foundation Security Advisory 2018-01 Speculative execution side-channel attack ("Spectre")

https://www.mozilla.org/en-US/security/advisories/mfsa2018-0...

You need to disable `SharedArrayBuffer` and `performance.now`, which Firefox already did.

chrome://flags/#enable-site-per-process is a mitigation that at least raises the bar a little. :/