The Speculative Execution Impact For A 4-Core POWER9 Blackbird Desktop

Written by Michael Larabel in Processors on 12 June 2019 at 05:20 PM EDT. Page 1 of 4. 13 Comments.

Last year we looked at the Spectre mitigation cost on POWER9 using the high-end Talos II server while now several kernel releases later and also having the desktop Blackbird system in our lab, here is a look at how the Spectre/Meltdown mitigation impact is for an IBM POWER9 4-core processor running Ubuntu 19.04.

Raptor Computing Systems ship their systems fully-mitigated by default for kernel and user-space protection in order to provide maximum security for the system. Fortunately, the mitigated impact isn't nearly as much as we've seen on Intel CPUs but is still measurable in relevant workloads. For those not concerned by the speculative execution vulnerabilities or not running untrusted code at all on the system, Raptor does make it easy to limit these protections to kernel-only or disabling the protections entirely.

If not familiar with the POWER9 speculative execution impact, see this Raptor Wiki page and the guide on configuring the protection level.

These benchmarks are being provided for reference figures for those curious about the mitigated performance impact using the Raptor Blackbird with IBM POWER9 4-core (16 thread) system with 128GB of RAM and 1TB Samsung MZVLB1T0HALR solid-state drive. This system was using Ubuntu 19.04 PowerPC with the Linux 5.0 kernel and GCC 8.3.0 code compiler. All of these POWER9 benchmarks were carried out using the Phoronix Test Suite.

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