How to improve latency on my D525 computer?

Ran latency-histogram for about 1 day
with 10 glxgears, stress and screensaver.
The local maximum near +-10us seems weird and I think it can be eliminated by some methods.
D525 is dual core, I disabled hyper-threading, removed xserver-xorg-video-intel so the display driver seems to be vesa.
isolcpus=1 kernel parameter added and set IRQ affinity to CPU0. What else can be done to improve latency?

How well does it work on your machine ?
The D525 is getting a bit old.
For lpt port stepping the Haswell Pentium G3258 has it all. Its cheap, unlocked for overclocking and still available.
srl

I think 20us aught to be good enough for software stepping, unless you need to go super fast or have a high micro-stepping count. And in those cases you should probably be considering hardware step generation anyway.

disable acpi / usb / lan / serial ports in bios