The Spectre/Meltdown Performance Impact On Linux 4.20, Decimating Benchmarks With New STIBP Overhead
Written by Michael Larabel in Software on 17 November 2018. Page 11 of 11. 60 Comments

Like with the Core i9 tests, the impact of Spectre/Meltdown mitigations are very noticeable for the memcached mcperf benchmark.

That's where the dual Intel Xeon server I frequently for use for benchmarking stands as of the latest Linux 4.20 Git code. It's quite surprising to see the additional performance overhead now presented by this new kernel code due to STIBP. We'll see what performance optimizations come about still for the Linux 4.20 cycle (if any) pertaining to this cross-HT Spectre V2 mitigation. Hopefully these tests will apply some extra urgency and pressure for optimizations as when this code was added during the Linux 4.20 cycle it did so without too much attention yet the performance impact is glaring.

We'll also see if AMD ends up needing STIBP or what's up on that front among other benchmarks to come in the days ahead. Fortunately even if the STIBP overhead can't be improved too much, at least Intel is closing in on the Cascade Lake Xeon launch where they are introducing new hardware-based Spectre and Meltdown mitigations. If you want to maximize your system/server performance today, the mitigations can be disabled if you so choose.

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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.


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