Testing Intel FSGSBASE Patches For Helping Elevate Linux Performance

[phoronix]

Phoronix: Testing Intel FSGSBASE Patches For Helping Elevate Linux Performance

After covering the Linux patches for FSGSBASE for years, it's looking like Linux 5.9 will finally land the support for this CPU capability present since Ivy Bridge on the Intel side and more recently on AMD CPUs with Bulldozer and Zen. Here are benchmarks looking at some of the performance benefits the Linux FSGSBASE patches can provide for an Intel Xeon Cascade Lake Refresh server.

http://www.phoronix.com/vr.php?view=29325

[davidbepo]

wonderful

[Volta]

Enable full mitigation and the we'll see.

Edit: chuckula, where is lvi mentioned?

[fguerraz]

But isn't the userspace software supposed to be modified to make use of it? I don't really understand, the patch doc says:

User-level programs (such as JAVA-based) may benefit from avoiding system calls to edit FS/GSBASE

Am I missing something?

[chuckula]

Enable full mitigation and the we'll see.

It clearly was enabled if you knew how to read the flags that were posted on the first page of the article.

[chuckula]

This is an amazing feature given that boosting I/O performance is always a big deal. It's just sad that it's taken 8 years for the feature to get turned on even in Linux, much less in other OS implementations.

[chuckula]

But isn't the userspace software supposed to be modified to make use of it? I don't really understand, the patch doc says:


Am I missing something?

It appears that there are ways to improve the results further in userspace, but since FSGSBASE makes context switching faster there are certainly performance benefits that don't require any changes to userspace code:

https://lwn.net/Articles/769355/

Benefits: Some performance benefit in context switch is expected by skipping MSR write for GSBASE.

[Michael]

This is an amazing feature given that boosting I/O performance is always a big deal. It's just sad that it's taken 8 years for the feature to get turned on even in Linux, much less in other OS implementations.

One thing I haven't seen is whether Windows already handles FSGSBASE?

[chuckula]

One thing I haven't seen is whether Windows already handles FSGSBASE?

You mentioned in one of your other articles that the work on FSGSBASE had attracted interest from Microsoft, which I take to mean that they haven't already implemented it:

https://www.phoronix.com/scan.php?page=news_item&px=FSGSBASE-v12-Linux-Patches

[Michael]

You mentioned in one of your other articles that the work on FSGSBASE had attracted interest from Microsoft, which I take to mean that they haven't already implemented it:

https://www.phoronix.com/scan.php?pa...-Linux-Patches

That was for pushing along the Linux patches by Sasha (presumably for Linux on Azure or their other related Linux interests) but not with regards to the Windows context.