SiSoftware Sandra 20/20/8 (2020 R8t) Update – JCC, bigLITTLE, Hypervisors + Future Hardware

Note: The original R8 release has been updated to R8t with future hardware support.

We are pleased to release R8t (version 30.61) update for Sandra 20/20 (2020) with the following updates:

Sandra 20/20 (2020) Press Release

JCC Erratum Mitigation

Recent Intel processors (SKL “Skylake” and later but not ICL “IceLake”) have been found to be impacted by the JCC Erratum that had to be patched through microcode. Naturally this can cause performance degradation depending on benchmark (approx 3% but up to 10%) but can be mitigated through assembler/compiler updates that prevent this issue from happening.

We have updated the tools with with which Sandra is built to mitigate JCC and we have tested the performance implications on both Intel and AMD hardware in the linked articles.

bigLITTLE Hybrid Architecture (aka “heterogeneous multi-processing”)

big.Little HMP
While bigLITTLE arch (including low and high-performance asymmetric cores into the same processor) has been used in many ARM processors, Intel is now introducing it to x86 as “Foveros”. Thus we have have Atom (low performance but very low power) and Core (high performance but relatively high power) into the same processor – scheduled to run or be “parked” depending on compute demands.

As with any new technology, it will naturally require operating system (scheduler) support and may go through various iterations. Do note that as we’ve discussed in our 2015 (!) article – ARM big.LITTLE: The trouble with heterogeneous multi-processing: when 4 are better than 8 (or when 8 is not always the “lucky” number) – software (including benchmarks) using all cores (big & LITTLE) may have trouble correctly assigning workloads and thus not use such processors optimally.

As Sandra uses its own scheduler to assign (benchmarking) threads to logical cores, we have updated it to allow users to benchmarks not only “All Threads (MT)” and “Only Cores (MC)” but also “Only big Cores (bMC)” and “Only LITTLE Cores (LMC)“. This way you can compare and contrast the various cores performance without BIOS/firmware changes.

The (benchmark) workload scheduler also had to be updated to allow per-thread workload – with threads scheduled on LITTLE cores assigned less work and threads on big cores assigned more work depending on their relative performance. The changes to Sandra’s workload scheduler allows each core can be fully utilised – at least when benchmarking.

Note: This advanced information is subject to change pending hardware and software releases and updates.

Future Hardware Support

Update R8t adds support for “Tiger Lake” (TGL) as well as updated support for “Ice Lake” (ICL) and future processors.

AMD Power/Performance Determinism

Some AMD’s server processors allow “determinism” to be changed to either “performance” (consistent speed across nodes/sockets) or “power” (consistent power across nodes/sockets). While normally workloads require predictability and thus “consistent performance” – this can be at the expense of speed (not taking advantage of power/thermal headroom for higher speed) and even power (too much power consumed by some sockets/nodes).

As “power deterministic” mode allows each processor at the maximum performance, there can be reasonable deviations across processors – but this would be unused if each thread has been assigned the same workload. In effect, it is similar to the “hybrid” issue above, with some cores able to sustain a different workload than other cores and the workload needs to vary accordingly. Again, the changes to Sandra’s workload scheduler allows each core to be fully utilised – at least when benchmarking.

Note: In most systems the deviation between nodes/sockets is relatively small if headroom (thermal/power) is small.

Hypervisors

More and more installations are now running in virtualised mode under a (Type 1) Hypervisor: using Hyper-V, Docker, programming tools for various systems (Android, etc.) or even enabling “Memory Integrity” all mean the system will be silently be modified to run in transparently under a hypervisor (Hyper-V on Windows).

As a result, Sandra will now detect and report hypervisor details when uploading benchmarks to the SiSoftware Official Live Ranker as even when running transparently/”host mode” – there can be deviation between benchmark scores especially when I/O operations (disk, network but even memory) are involved; some mitigations for vulnerabilities apply to both the hypervisor and host/guest operating system with a “double-impact” to performance.

Note: We will publish an article detailing the deviation seen with different hypervisors (Hyper-V, VmWare, Xen, etc.).

Reviews using Sandra 20/20:

Update & Download

Commercial version customers can download the free updates from their software distributor; Lite users please download from your favourite download site.

Download Sandra Lite

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