Re: [PATCH v2] x86/irq: Optimize interrupts decimals printing

[Dmitry Ilvokhin]

I would like to follow up on this patch with additional data from production
deployment.

We have rolled out this change to a subset of the Meta fleet. On each machine,
dynolog [1] periodically reads /proc/interrupts to collect per-CPU interrupt
statistics, so this path executes frequently across the fleet.

After deploying the patch, we measured the reduction in CPU cycles
spent in the /proc/interrupts read path on machines with different
virtual core counts.

vCores   Cycle reduction
------   ---------------
36          -18.9%
72          -25.5%
252         -34.7%

As expected, the benefit increases with higher core counts, since the
formatting work scales with the number of CPUs.

We have not observed any functional regressions or changes in the output
format. Existing userspace parsers continue to work without
modification.

Please let me know if there are any concerns or if additional data would be
helpful.

[1]: https://github.com/facebookincubator/dynolog