Performance did not get substantially worse yet since last reboot on January 29th.
My guess one of these things could help:
----We ran UPDATE STATISTICS 2-3 times since last reboot
----Moved Transaction Log file of one of busy databases to a proper drive (before it was sitting together with data files)
Maybe I was wrong when said performance gradually gets worse.
I'm afraid it might be pretty sudden.
Like 2-3 days of slower than usual and then big slowdown.
We don't see a big Disk latency now. Like we saw last time before reboot.
Overall it stays on the same level it was right after reboot.
Again, the size of the files for TempDB are a pretty good clue that some poorly formed code has reached a "tipping point" due to the ever increasing scale of data. That code needs to be identified and repaired.