Intel Resurrecting FSGSBASE Support For Linux To Help With Performance

[phoronix]

Phoronix: Intel Resurrecting FSGSBASE Support For Linux To Help With Performance

Going on for months had been work by Intel Linux developers on supporting the FSGSBASE instruction for helping Intel CPU performance going back to Ivybridge where this instruction set extension was first introduced. The FSGSBASE support was queued for the Linux 5.3 kernel but was reverted due to "serious bugs" in the implementation. Intel has now published a revised version of this support...

http://www.phoronix.com/scan.php?page=news_item&px=Intel-FSGSBASE-Resurrected

[perpetually high]

Heck yeah, more patches! I'm gonna be a guinea pig and give these a whirl on my Haswell machine.

Looking through one of the patch diffs:

- unsafe_fsgsbase [X86] Allow FSGSBASE instructions. This will be
- replaced with a nofsgsbase flag.
+ nofsgsbase [X86] Disables FSGSBASE instructions.

It looks like it's enabled by default with these patches, and you can use the nofsgsbase kernel parameter to disable it.

EDIT: ran a couple preliminary Geekbench 5 benchmarks for a ballpark:

with FSGSBASE:

first run: 1138 single-core, 4051 multi-core
second run: 1143 single-core, 4007 multi-core

without FSGSBASE:

first run: 1145 single-core, 4027 multi-core
second run: 1145 single-core, 4005 multi-core

All tests used the performance governor and were run with the command: nice -n -4 ./geekbench5

[perpetually high]

Hey Michael, I noticed v9 of the patchset was released on Oct. 4. Not sure if you want to cover it now as it is a month old and likely v10 will be coming soon, but just a heads up.