Backup variations after Spectre/Meltdown

I applied the 2/22 and 2/8 Spectre/Meltdown fixes (https://www-01.ibm.com/support/docview.wss?uid=nas8N1022433) on the 26th. Since then, I've been seeing some variations in my nightly backup. I have stats back thru 2/1, and it didn't appear before these PTF's.

I use virtual tape and some nights it's taking 2-3 minutes longer than normal (but other nights are normal). The difference appears to be related to CPI6705 messages in the joblog. For a static library, one night the CPI6705 will take 4 seconds and the next night 27 seconds. Some other libraries that do change also show the same variation, but the overall size of those libraries doesn't really change.

For example:

Friday:
20:03:50 CPC3701 Completion 00 69 Objects saved from #LIBRARY
20:03:54 CPI6705 Information 00 2447 blocks processed for sequence 9, volume BKUP, on device T3.
20:03:54 CPI6705 Information 00 2 blocks processed for sequence 10, volume BKUP, on device T3.

Monday:
20:03:36 CPC3701 Completion 00 69 Objects saved from #LIBRARY
20:04:03 CPI6705 Information 00 2447 blocks processed for sequence 9, volume BKUP, on device T3.
20:04:03 CPI6705 Information 00 2 blocks processed for sequence 10, volume BKUP, on device T3.



TIA