Make dpaa2 cleanup budget values configurable

[flo_purplekraken.com]

Summary

Make hard-coded values available as sysctl tunables.

[dsl]

sys/dev/dpaa2/dpaa2_ni.c

455

We've the only budget here, so "budget" would be shorter. Besides, consider making it read-only with "const int". It doesn't look like the variable itself is written in the function.

456

same here

1810

Could you re-write with SYSCTL_ADD_PROC as for "buf_num" and "buf_free"? You already know how not only to read, but to write a value from sysctl ;)

1813

Should be "&sc->tx_budget", I guess

1815

Should be "&sc->rx_budget", I guess

2890

Please, declare local variables for the budgets like "uint32_t buf_num = DPAA2_ATOMIC_READ(&sc->buf_num);" and use them instead of those kept in the sc. It'd help to avoid inconsistency when someone modifies sysctl while the cleanup task is running.

sys/dev/dpaa2/dpaa2_ni.h

488

There's a sysctl(9) section below in the same sc with "buf_num" and "buf_free". Put those guys there, please. Besides, I'd still prefer "struct dpaa2_atomic" for the budget variables. It might not be necessary for the 32-bit signed variables which will probably by read/written atomically on ARM64, but I just want to be sure.

P.S. This is exactly the reason why full -U999999 context is needed ;)

[flo_purplekraken.com]

sys/dev/dpaa2/dpaa2_ni.c

455

The implementation contains a local variable called budget. I can of course rename the parameter, but then I have to rename the local variable, too.

1810

If I understood the documentation correctly, the SYSCTL_ADD_INT() functions do support reading and writing the value, but they do nothing else, like calling update functions. But since I will change the variable type to dpaa2_atomic, I have to use custom handlers anyway.

[flo_purplekraken.com]

• Make sysctl storage values atomic
• Group sysctl values

[flo_purplekraken.com]

sys/dev/dpaa2/dpaa2_ni.h

488

Extra context added with this patch.

[dsl]

sys/dev/dpaa2/dpaa2_ni.c

2903

Budgets aren't written in the rest of the function, i.e. "const int" please.

3618

Please, declare the function at the top of the file. And a short comment what it does would be handy as I struggled a bit initially.

3629

I'd move hardcoded values to the macros. Something like "...BUDGET_MIN" and "...BUDGET_MAX".

[flo_purplekraken.com]

sys/dev/dpaa2/dpaa2_ni.c

3629

Are these plaubsible and useful limits?

[dsl]

sys/dev/dpaa2/dpaa2_ni.c

3629

Yes, I think so. At the moment, at least.

[dsl]

Could you rebase to the latest main as well as it doesn't apply cleanly with https://reviews.freebsd.org/D59463 pushed?

[flo_purplekraken.com]

• Make local variables read from atomics const.
• Extract magic numbers to preprocessor defines.
• Add declaration and comment to sysctl helper function.