Humungus, Im experiencing the exact same battery drain as you. ksoftirqd is using alot of CPU time. Im on 1.8.9 coming from 1.8.6. I installed and wiped only cache. Everything is very snappy. The only down side being my battery life now. I considered wiping data and cache as I usually have but others have reported getting bad battery regardless of whether they wipe or not. Any idea of how this can be fixed?
Update:
I cleaned out my sdcard by copying everything to my desktop, formatting the sdcard from within 'settings' and copying back just my media and backup stuff (music, notification sounds, wallpapers, apps and roms). I then reinstalled 1.9.3 after wiping data, wiping cache, formatting system, and installing .zip.
After booting up I let Google reinstall all of my apps, and so far the problem seems to have gone away. It's now been 2.5 hours and I just went down to 80% (keep in mind that the first 30 minutes after an install involve heavy downloading, installing, and configuring). ksoftirqd has accounted for only 3% of use, which doesn't strike me as ridiculously out of whack (though it could still be). I haven't restored app data with Titnanium yet, so we'll see if things go down hill after that.
I suggest doing the same with 1.8.9.