Patch Posted To Enable Intel FRED By Default On Linux
Following today's article exploring the performance benefits of Intel Flexible Return and Event Delivery "FRED" with Panther Lake and also pointing out the rather obscure nature of FRED being disabled-by-default, an Intel Linux kernel engineer posted a patch to now enable FRED by default for better performance.
Longtime Linux engineer H. Peter Anvin with Intel posted the patch to enable FRED by default on supported processors. FRED so far is found with Core Ultra Series 3 "Panther Lake" plus upcoming Xeon Diamond Rapids processors. AMD Zen 6 processors are also expected to support FRED.
The rationale in today's patch for having FRED disabled-by-default until now was "risk of regressions before hardware was available publicly." But now that Panther Lake is out in the wild and our benchmarks have shown it to be a win, it's time to change that default. H. Peter Anvin commented with the patch:
The patch is out for review on the Linux kernel mailing list. Given the timing of the patch, this change will presumably be queued in time for next month's Linux 7.1 merge window. Too bad that it's late in the Linux 7.0 cycle for this kernel that will be used by default on the likes of Ubuntu 26.04 LTS. As noted in today's earlier article, anyone on a recent Linux kernel release can enable FRED with Panther Lake via the fred=on boot parameter.
Longtime Linux engineer H. Peter Anvin with Intel posted the patch to enable FRED by default on supported processors. FRED so far is found with Core Ultra Series 3 "Panther Lake" plus upcoming Xeon Diamond Rapids processors. AMD Zen 6 processors are also expected to support FRED.
👁 FRED on Intel Panther Lake laptop
The rationale in today's patch for having FRED disabled-by-default until now was "risk of regressions before hardware was available publicly." But now that Panther Lake is out in the wild and our benchmarks have shown it to be a win, it's time to change that default. H. Peter Anvin commented with the patch:
"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:
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 patch is out for review on the Linux kernel mailing list. Given the timing of the patch, this change will presumably be queued in time for next month's Linux 7.1 merge window. Too bad that it's late in the Linux 7.0 cycle for this kernel that will be used by default on the likes of Ubuntu 26.04 LTS. As noted in today's earlier article, anyone on a recent Linux kernel release can enable FRED with Panther Lake via the fred=on boot parameter.