A Dummy Wait Op Has Been Unnecessarily Slowing AMD Chips
Should you’ve run into workloads in your AMD powered Linux field which are slower than anticipated, a repair is on the way in which to make your life higher. There may be an historical workaround which was wanted to make sure some chipsets had time for STPCLK# assertions, which dates again to 2002 when Linux first included ACPI assist. This was completed with a dummy wait op that gave outdated chipsets, like these from VIA, sufficient time to correctly end operations earlier than transferring on.
The issue is that it hasn’t been essential in fairly a while, but it surely was by no means eliminated. This doesn’t have an enormous impact on a small Ryzen system, nevertheless it additionally applies to EPYC processors. That implies that even a small delay can add up if you deploy these chips at scale. The repair has simply been merged into Linux 6.0 which implies that Phoronix must get busy benchmarking.
You’ll be able to learn particulars about why this repair was essential for AMD ACPI right here, with benchmarks to comply with quickly.