Hi,

I've been hunting down some hackbench regression between 5.4-rc8 and 5.5-rc1 on my Juno r0, one of the offenders seems to be:

246880958ac9 ("firmware: broadcom: add OP-TEE based BNXT f/w manager")

This is tested on a kernel built with defconfig (TEE_BNXT_FW gets selected) and with:

echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor echo performance > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor ./perf stat --null --sync --repeat 200 ./hackbench

The regression is easily reproducible on my end, this is 3 runs of the above comparing the patch and its parent:

-PATCH: 0.71062 +- 0.00150 seconds time elapsed ( +- 0.21% ) 0.71121 +- 0.00181 seconds time elapsed ( +- 0.25% ) 0.71277 +- 0.00181 seconds time elapsed ( +- 0.25% )

+PATCH: 0.72556 +- 0.00174 seconds time elapsed ( +- 0.24% ) 0.72695 +- 0.00192 seconds time elapsed ( +- 0.26% ) 0.72559 +- 0.00178 seconds time elapsed ( +- 0.25% )

AIUI Vincent found something different while hunting down a similar regression:

df323337e507 ("apparmor: Use a memory pool instead per-CPU caches")

but it seems this one is another cause. Seeing as this involves security stuff the overhead may be acceptable, nevertheless now that I have some reproducer I figured I'd send this out.

Cheers, Valentin