3.5GBとは何ですかこのシステムのメモリ使用量は「[ヒープ]」（666M）ではありませんか？

$ sudo smem -t -m > m; head -n5 m; echo; tail m

Map                                       PIDs   AVGPSS      PSS 
/dev/dri/card0                               2        0        0 
/dev/shm/org.chromium.0P27rF                 1        0        0 
/dev/shm/org.chromium.1LwGBc                 1        0        0 
/dev/shm/org.chromium.23Bqe3                 1        0        0 

/dev/shm/org.mozilla.ipc.23887.6343          2     6772    13544 
/dev/shm/org.mozilla.ipc.23935.491           2     6772    13544 
/memfd:gdk-wayland                           6     2890    17344 
/SYSV00000000                                6     3759    22556 
/usr/lib64/firefox/libxul.so                14     8711   121956 
/i915                                        4    38494   153976 
[heap]                                     208     3201   665971 
<anonymous>                                222    15859  3520738 
-----------------------------------------------------------------
1698                                     20333   280628  5056008

「[ヒープ]」（666M）を除いて、このシステムで3.5GBの「<anonymous>」メモリ使用量はいくらですか？

フルShmem（すべてのtmpfsファイルとジュエリーバッファ）は約608M（「608004kB」）に「のみ」です。

$ uname -r  # Kernel version
5.0.17-200.fc29.x86_64

$ cat /proc/meminfo
MemTotal:        8042664 kB
MemFree:          426436 kB
MemAvailable:    2521060 kB
Buffers:          266884 kB
Cached:          2576424 kB
SwapCached:        14624 kB
Active:          4242740 kB
Inactive:        2647644 kB
Active(anon):    3097748 kB
Inactive(anon):  1561596 kB
Active(file):    1144992 kB
Inactive(file):  1086048 kB
Unevictable:      203436 kB
Mlocked:           13700 kB
SwapTotal:       2097148 kB
SwapFree:        1472816 kB
Dirty:               112 kB
Writeback:             0 kB
AnonPages:       4241276 kB
Mapped:           760472 kB
Shmem:            608004 kB
KReclaimable:     165768 kB
Slab:             332388 kB
SReclaimable:     165768 kB
SUnreclaim:       166620 kB
KernelStack:       21552 kB
PageTables:        47628 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     6118480 kB
Committed_AS:   15395448 kB
VmallocTotal:   34359738367 kB
VmallocUsed:           0 kB
VmallocChunk:          0 kB
Percpu:             3424 kB
HardwareCorrupted:     0 kB
AnonHugePages:   1796096 kB
ShmemHugePages:        0 kB
ShmemPmdMapped:        0 kB
CmaTotal:              0 kB
CmaFree:               0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
Hugetlb:               0 kB
DirectMap4k:      483892 kB
DirectMap2M:     7782400 kB
DirectMap1G:     1048576 kB