Last week I ran [1]benchmarks quantify the performance benefit to Intel FRED for Flexible Return and Event Delivery initially found with the new Core Ultra Series 3 "Panther Lake" processors and also for upcoming Nova Lake and Diamond Rapids CPUs. The FRED performance impact was very beneficial across a variety of workloads but rather strangely was not enabled by default. Mere hours after publishing that article, [2]an Intel engineer posted a patch to enable FRED by default . Now this week that patch appears all-set for merging with the upcoming Linux 7.1 merge window.

With the great performance gains found out of the Intel Core Ultra X7 358H when manually enabling FRED via the fred=on kernel parameter, it was puzzling that this wasn't enabled by default especially with Panther Lake laptops now shipping for the past two months. Intel engineers squared away the rest of the FRED support for the Linux kernel a while ago and given the significant performance benefit it's baffling that it wasn't enabled pre-launch. The past last week though characterized the non-default state as waiting on production hardware for validating the performance impact and ensuring no regressions.

"When FRED was added to the mainline kernel, it was set up as an explicit opt-in due to the risk of regressions before hardware was available publicly.

Now, Panther Lake (Core Ultra 300 series) has been released, and benchmarking by Phoronix has shown that it provides a significant performance benefit on most workloads:

[3]https://www.phoronix.com/review/intel-fred-panther-lake

Accordingly, enable FRED by default if the CPU supports it. FRED can of course still be disabled via the fred=off command line option."

The news today is that the patch has been queued into [4]tip/tip.git's x86/fred Git branch . With the patch now in a TIP branch, it should be submitted for the Linux 7.1 merge window happening in April following the Linux 7.0 stable release. Too bad this wasn't sorted out in time for the Linux 7.0 kernel merge window so it would be the default in the likes of Ubuntu 26.04 LTS, but at least it happened now in time for v7.1.

So look for better performance with Panther Lake and future Intel CPUs plus AMD Zen 6 with Linux 7.1+ with FRED being enabled by default. Those on Panther Lake with recent kernel versions can still boot for now with fred=on to enjoy the added performance of Flexible Return and Event Delivery.



[1] https://www.phoronix.com/review/intel-fred-panther-lake

[2] https://www.phoronix.com/news/Intel-FRED-By-Default-Patch

[3] https://www.phoronix.com/review/intel-fred-panther-lake

[4] https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=ac66a73be03a0a72aeeb33d3610cfc43cb101a0b