I did a very crude test using 3D Mark 11 and Unigine "Heaven" to see just how much effect that Antivirus / Malware software have on the performance of my GTX 1080 SC2.  Tested at default Precision settings for Power and Temp target...100/83 and 120 / 92
 
I use both Trend Micro Maximum security and Malwarebytes 3.06
 
Here are some scores....maybe some of you can add to this list:
 
100/83                                                                                            120/92
 
3DM11 with TM and MWB   18,380                                                     18,734
w/o TM / MWB enabled       22,978                                                     23,167
w/o TM or MWB                 22,942                                                     23,169
 
Heaven with TM/MWB          2991                                                        3034
H w/o TM MWB enabled       3029                                                         3039
w/o TM or MWB                   3028                                                        3043
 
Based on this crude test...I can attest that Trend Micro scans while running the programs and games and slows the GPU down.  Malwarebytes shows no effect on programs.  I did one other settings with Trend Micro enabled.  I added Futuremark folder and Unigine folders to the exception list, so they don't get scanned during use...and both performed to the same level as with Trend Micro disabled.  Having used Kaspersky and Bitdefender in the past, I wonder if "Game Mode" would have an impact on the scores.  What do you use? 
 
Just some food for thought.  Maybe either do the exception list additions or disable your AV during gaming.  I also added my Origin / Steam and Uplay folders to exception.