Tiny Linux Patch Up To 32% Faster, Up To 18% Less Energy For Intel Xeon Emerald Rapids
Canonical engineer Pedro Henrique Kopper sent a patch Thursday to the Linux kernel mailing list for updating the balance performance Energy Performance Preference (EPP) for Intel Xeon Scalable "Emerald Rapids" processors. Pedro wrote on the patch:
On Intel Emerald Rapids machines, we ship the Energy Performance Preference (EPP) default for balance_performance as 128. However, during an internal investigation together with Intel, we have determined that 32 is a more suitable value. This leads to significant improvements in both performance and energy:
POV-Ray: 32% faster | 12% less energy
OpenSSL: 12% faster | energy within 1%
Build Linux Kernel: 29% faster | 18% less energy
Therefore, we should move the default EPP for balance_performance to 32. This is in line with what has already been done for Sapphire Rapids.
It's important to note that this change is for the EPP "balance_performance" mode as used by default out-of-the-box on Ubuntu Linux and various other Linux distributions but doesn't impact for those switching over to the "performance" setting. In any event up to 32% faster performance and up to 18% less energy while enjoying these gains is very significant.
It's a bit embarrassing that this wasn't caught months ago with Emerald Rapids being out since last year and this one line patch is just carrying over the EPP value found for similar Intel Sapphire Rapids processors. There should also be performance and power efficiency gains in other workloads but it was just these three PTS benchmarks that Canonical/Intel was using for evaluation.
This also isn't the first time EPP adjustments post-launch have paid off as over the summer EPP tuning had a big win for Intel Meteor Lake too.
In any event the issue is now known, the patch is out there for the Intel P-State Linux CPU frequency scaling driver, and will hopefully be picked up for the Linux 6.12 kernel. (Update: Linux PM maintainer Rafael Wysocki has commented he intends to submit this patch for the current Linux 6.11 cycle within the next week or two, rather than waiting for Linux 6.12.)
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