在 Linux(RedHat) 中，C function malloc_stats() 显示与 /proc/ 不同的值<pid> /stat 常驻 memory 大小</pid>

Question

eg For a process running in Redhat linux as per /proc/{pid}/stat's resident pages * page size => 30 GB

as per malloc_stats() => 2.5 GB

any idea why this happens?

Arena 0:
system bytes     =  465162240
in use bytes     =  465037200
Arena 1:
system bytes     =    1003520
in use bytes     =     980656
Arena 2:
system bytes     =    8065024
in use bytes     =    7771728
Arena 3:
system bytes     = 2278395904
in use bytes     = 2276584320
Arena 4:
system bytes     =    1482752
in use bytes     =    1236112
Arena 5:
system bytes     =    1482752
in use bytes     =    1235440
Arena 6:
system bytes     =    1482752
in use bytes     =    1240512
Total (incl. mmap):
system bytes     = 2782,699,520
in use bytes     = 2779710544
max mmap regions =          9
max mmap bytes   =   25624576

Answer 1

malloc_stats is tied to the implementation of malloc in user-land.

pmap or /proc/self/stat is related to the virtual address space and its perception in kernel land, which changes not only with mmap called by malloc but also with other calls to mmap , including those related to the dynamic linker ( ld.so )

Read a good textbook on operating systems . See also https://linuxatemyram.com/ and proc(5) , mmap(2) , execve(2) , malloc(3)