from: ars technica (Here’s how, and why, the Spectre and Meltdown patches will hurt performance | Ars Technica ) The overhead of a few percent assumes that workloads are standard desktop workloads; browsers, games, productivity applications, and so on. These workloads don't actually call into the kernel very often, spending most of their time in the application itself (or idle, waiting for the person at the keyboard to actually do something). Tasks that use the disk or network a lot will see rather more overhead. This is very visible in TechSpot's benchmarks. Compute-intensive workloads such as Geekbench and Cinebench show no meaningful change at all. Nor do a wide range of games. But fire up a disk benchmark and the story is rather different. Both CrystalDiskMark and ATTO Disk Benchmark show some significant performance drop-offs under high levels of disk activity, with data transfer rates declining by as much as 30 percent. That's because these benchmarks do virtually nothing other than issue back-to-back calls into the kernel. Phoronix found similar results in Linux: around a 12-percent drop in an I/O intensive benchmark such as the PostgreSQL database's pgbench but negligible differences in compute-intensive workloads such as video encoding or software compilation.
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