ArenaTest.UnmappedAllocation fails when "transparent hugepage" is enabled.

[v01dstar]

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Expected behavior

All tests pass on my desktop.

                   -`                    v01dstar@arch 
                  .o+`                   ------------- 
                 `ooo/                   OS: Arch Linux x86_64 
                `+oooo:                  Kernel: 6.7.2-arch1-2 
               `+oooooo:                 Uptime: 3 days, 57 mins 
               -+oooooo+:                Packages: 729 (pacman) 
             `/:-:++oooo+:               Shell: fish 3.7.0 
            `/++++/+++++++:              Resolution: 1440x2560, 2560x1440 
           `/++++++++++++++:             WM: i3 
          `/+++ooooooooooooo/`           Theme: Adwaita [GTK3] 
         ./ooosssso++osssssso+`          Icons: Adwaita [GTK3] 
        .oossssso-````/ossssss+`         Terminal: kitty 
       -osssssso.      :ssssssso.        CPU: AMD Ryzen 9 5900X (24) @ 3.700GHz 
      :osssssss/        osssso+++.       GPU: AMD ATI Radeon RX 6400/6500 XT/6500M 
     /ossssssss/        +ssssooo/-       GPU: NVIDIA GeForce RTX 3080 Lite Hash Rate 
   `/ossssso+/:-        -:/+osssso+-     Memory: 9632MiB / 64210MiB 
  `+sso+:-`                 `.-/+oso:
 `++:.                           `-/+/                           
 .`                                 `/                           

v01dstar@arch ~> cat /sys/kernel/mm/transparent_hugepage/enabled
[always] madvise never

Actual behavior

ArenaTest.UnmappedAllocation fails. (It passes if I change THP to madvise or never).

Steps to reproduce the behavior

Run the test case with THP enabled (always). On my friend's Ubuntu, he also need to set sysctl -w vm.nr_hugepages=256 to reproduce the failure.

This test case expects on-demand Arena paging allocation (IIUC from the PR that introduced it), but seems, it needs to be composed conditionally based on OS, hardware's settings.