FYI, we noticed the below changes on

commit f5b2831d654167d77da8afbef4d2584897b12d0c ("x86: Respect PAT bit when copying pte values between large and normal pages")

This may be the expected behavior.

testbox/testcase/testparams: lkp-nex04/boot/performance-1

f439c429c3209819  f5b2831d654167d77da8afbef4  
----------------  --------------------------  
         %stddev     %change         %stddev
             \          |                \  
      6584 ±  0%     +93.3%      12728 ±  0%  boot-meminfo.DirectMap4k
     41.19 ±  1%      +2.1%      42.05 ±  0%  boottime.dhcp


                              boot-meminfo.DirectMap4k

  13000 ++------------------------------------------------------------------+
        O O  O O  O O  O O O  O O  O O  O O O  O O  O O  O O O  O O  O O    |
  12000 ++                                                                  |
        |                                                                   |
  11000 ++                                                                  |
        |                                                                   |
  10000 ++                                                                  |
        |                                                                   |
   9000 ++                                                                  |
        |                                                                   |
   8000 ++                                                                  |
        |                                                                   |
   7000 *+*..*.                                                             |
        |      *..*.*..*.*.*..*.*..*.*..*.*.*..*.*..*.*..*.*.*..*.*..*.*..*.*
   6000 ++------------------------------------------------------------------+


        [*] bisect-good sample
        [O] bisect-bad  sample

Best Regards,
Huang, Ying