On 30 Jan 2026, at 9:47, Chuck Lever wrote:

On Fri, Jan 30, 2026, at 8:25 AM, Benjamin Coddington wrote:

quoted

I could, if it pleases everyone, do a function profile for fh_append_mac and
fh_verify_mac

Trond or Mike can demonstrate for you how to capture flame graphs
to very graphically illustrate how much CPU utilization is introduced
when using this feature. It would be valuable to confirm our expectation
that the additional CPU consumption will essentially be in the noise.

Here's a flame graph of a client doing 10 passes at a directory with 10k
files, looking them up and then doing GETATTR on each.  Each pass starts
with an empty cache.

https://bcodding.com/signfh_cpu_flame_graph/perf.svg

You'll want to look for fh_append_mac and fh_verify_mac.

Easier to find fh_append_mac by zooming to nfsd4_proc_compound:
https://bcodding.com/signfh_cpu_flame_graph/perf.svg?s=fh_append_mac&x=65.2&y=757

Easier to find fh_verify_mac by zooming to nfsd4_putfh:
https://bcodding.com/signfh_cpu_flame_graph/perf.svg?s=fh_verify_mac&x=537.9&y=741

This profile was filtered to only show events for the nfsd threads, and the
two functions needed to be annotated to remove the compiler optimizations in
order to show them in the profile.  This on a VM running in VMWare Fusion on
an arm64 Macbook Pro.

Ben