Resilver in progress & sysctl changes -- immediate effect?

[dodgeandburn]

I've seen many posts about speeding up resilvering, but I have not so far found if changes to the sysctl tunables are expected to have an immediate effect. I have changed a few (as documented here), but the resilvering speed doesn't appear to be changing in zpool status. Do they need to be in place before a resilver starts?

Thanks