linux如何对c++进行内存分析
- 背景
- 分析方法以及原理
- 原理
- 分析结果以及重点关注
背景
在工作中，我遇到一个问题，需要将c写的进程部署到MCU上。由于MCU上可用的RAM 非常有限，所以在部署时就需要考虑到使用内存大小。所以为了搞清楚，内存的主要消耗在那一块。
分析方法以及原理
原理
在linux 中每个进程在proc 中都有一个对应的文件存储其重要信息。其命令如下：
#!/bin/bash
pid=`ps -ef | grep process_name` # 找到pid
cat /proc/${pid}/smaps # 这个文件中存储该进程的所有内存映射
其结果如下这是一个例子:
5d76f76fb000-5d76f76fc000 r--p 00000000 08:03 3721356 /home/lhd/fastdds_repo/tmp/micro-dds-client/micro_client/examples/SubscribeHelloWorld/build/SubscribeHelloWorldClient
Size: 4 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 4 kB
Pss: 4 kB
Pss_Dirty: 4 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 4 kB
Referenced: 4 kB
Anonymous: 0 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd mr mw me sd
5d76f76fc000-5d76f7705000 r-xp 00001000 08:03 3721356 /home/lhd/fastdds_repo/tmp/micro-dds-client/micro_client/examples/SubscribeHelloWorld/build/SubscribeHelloWorldClient
Size: 36 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 36 kB
Pss: 36 kB
Pss_Dirty: 36 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 36 kB
Referenced: 36 kB
Anonymous: 0 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd ex mr mw me sd
5d76f7705000-5d76f770b000 r--p 0000a000 08:03 3721356 /home/lhd/fastdds_repo/tmp/micro-dds-client/micro_client/examples/SubscribeHelloWorld/build/SubscribeHelloWorldClient
Size: 24 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 24 kB
Pss: 24 kB
Pss_Dirty: 24 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 24 kB
Referenced: 24 kB
Anonymous: 0 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd mr mw me sd
5d76f770b000-5d76f770c000 r--p 0000f000 08:03 3721356 /home/lhd/fastdds_repo/tmp/micro-dds-client/micro_client/examples/SubscribeHelloWorld/build/SubscribeHelloWorldClient
Size: 4 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 4 kB
Pss: 4 kB
Pss_Dirty: 4 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 4 kB
Referenced: 4 kB
Anonymous: 4 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd mr mw me ac sd
5d76f770c000-5d76f770d000 rw-p 00010000 08:03 3721356 /home/lhd/fastdds_repo/tmp/micro-dds-client/micro_client/examples/SubscribeHelloWorld/build/SubscribeHelloWorldClient
Size: 4 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 4 kB
Pss: 4 kB
Pss_Dirty: 4 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 4 kB
Referenced: 4 kB
Anonymous: 4 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd wr mr mw me ac sd
5d76f965c000-5d76f967d000 rw-p 00000000 00:00 0 [heap]
Size: 132 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 4 kB
Pss: 4 kB
Pss_Dirty: 4 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 4 kB
Referenced: 4 kB
Anonymous: 4 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd wr mr mw me ac sd
7b4483e00000-7b4483e28000 r--p 00000000 08:03 7603927 /usr/lib/x86_64-linux-gnu/libc.so.6
Size: 160 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 160 kB
Pss: 1 kB
Pss_Dirty: 0 kB
Shared_Clean: 160 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 160 kB
Anonymous: 0 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd mr mw me sd
7b4483e28000-7b4483fbd000 r-xp 00028000 08:03 7603927 /usr/lib/x86_64-linux-gnu/libc.so.6
Size: 1620 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 1156 kB
Pss: 9 kB
Pss_Dirty: 0 kB
Shared_Clean: 1156 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 1156 kB
Anonymous: 0 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd ex mr mw me sd
7b4483fbd000-7b4484015000 r--p 001bd000 08:03 7603927 /usr/lib/x86_64-linux-gnu/libc.so.6
Size: 352 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 168 kB
Pss: 1 kB
Pss_Dirty: 0 kB
Shared_Clean: 168 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 168 kB
Anonymous: 0 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd mr mw me sd
7b4484015000-7b4484016000 ---p 00215000 08:03 7603927 /usr/lib/x86_64-linux-gnu/libc.so.6
Size: 4 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 0 kB
Pss: 0 kB
Pss_Dirty: 0 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 0 kB
Anonymous: 0 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: mr mw me sd
7b4484016000-7b448401a000 r--p 00215000 08:03 7603927 /usr/lib/x86_64-linux-gnu/libc.so.6
Size: 16 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 16 kB
Pss: 16 kB
Pss_Dirty: 16 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 16 kB
Referenced: 16 kB
Anonymous: 16 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd mr mw me ac sd
7b448401a000-7b448401c000 rw-p 00219000 08:03 7603927 /usr/lib/x86_64-linux-gnu/libc.so.6
Size: 8 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 8 kB
Pss: 8 kB
Pss_Dirty: 8 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 8 kB
Referenced: 8 kB
Anonymous: 8 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd wr mr mw me ac sd
7b448401c000-7b4484029000 rw-p 00000000 00:00 0
Size: 52 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 20 kB
Pss: 20 kB
Pss_Dirty: 20 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 20 kB
Referenced: 20 kB
Anonymous: 20 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd wr mr mw me ac sd
7b448419c000-7b448419f000 rw-p 00000000 00:00 0
Size: 12 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 8 kB
Pss: 8 kB
Pss_Dirty: 8 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 8 kB
Referenced: 8 kB
Anonymous: 8 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd wr mr mw me ac sd
7b44841b4000-7b44841b6000 rw-p 00000000 00:00 0
Size: 8 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 4 kB
Pss: 4 kB
Pss_Dirty: 4 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 4 kB
Referenced: 4 kB
Anonymous: 4 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd wr mr mw me ac sd
7b44841b6000-7b44841b8000 r--p 00000000 08:03 7602987 /usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2
Size: 8 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 8 kB
Pss: 0 kB
Pss_Dirty: 0 kB
Shared_Clean: 8 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 8 kB
Anonymous: 0 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd mr mw me sd
7b44841b8000-7b44841e2000 r-xp 00002000 08:03 7602987 /usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2
Size: 168 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 168 kB
Pss: 1 kB
Pss_Dirty: 0 kB
Shared_Clean: 168 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 168 kB
Anonymous: 0 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd ex mr mw me sd
7b44841e2000-7b44841ed000 r--p 0002c000 08:03 7602987 /usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2
Size: 44 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 40 kB
Pss: 0 kB
Pss_Dirty: 0 kB
Shared_Clean: 40 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 40 kB
Anonymous: 0 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd mr mw me sd
7b44841ee000-7b44841f0000 r--p 00037000 08:03 7602987 /usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2
Size: 8 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 8 kB
Pss: 8 kB
Pss_Dirty: 8 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 8 kB
Referenced: 8 kB
Anonymous: 8 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd mr mw me ac sd
7b44841f0000-7b44841f2000 rw-p 00039000 08:03 7602987 /usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2
Size: 8 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 8 kB
Pss: 8 kB
Pss_Dirty: 8 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 8 kB
Referenced: 8 kB
Anonymous: 8 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd wr mr mw me ac sd
7ffd2ac21000-7ffd2acc7000 rw-p 00000000 00:00 0 [stack]
Size: 664 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 664 kB
Pss: 664 kB
Pss_Dirty: 664 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 664 kB
Referenced: 664 kB
Anonymous: 664 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd wr mr mw me gd ac
7ffd2ad1b000-7ffd2ad1f000 r--p 00000000 00:00 0 [vvar]
Size: 16 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 0 kB
Pss: 0 kB
Pss_Dirty: 0 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 0 kB
Anonymous: 0 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd mr pf io de dd sd
7ffd2ad1f000-7ffd2ad21000 r-xp 00000000 00:00 0 [vdso]
Size: 8 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 4 kB
Pss: 0 kB
Pss_Dirty: 0 kB
Shared_Clean: 4 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 4 kB
Anonymous: 0 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd ex mr mw me de sd
ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0 [vsyscall]
Size: 4 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 0 kB
Pss: 0 kB
Pss_Dirty: 0 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 0 kB
Anonymous: 0 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: ex
单个内存映射分析
VmFlags: rd wr mr mw me ac sd
这一行列出了与该内存映射相关联的虚拟内存标志（VmFlags）。不过，这些标志的具体含义在不同的上下文中可能有所不同，且并非所有系统都会以这种方式列出它们。通常，这些标志包括读（rd）、写（wr）、执行（me，但这里可能是ex的简写，因为me不是常见的标准标志）、访问（ac，表示该内存区域已被访问）、共享（sh，但这里用的是sd，可能是特定于系统的缩写或错误）等。然而，mr和mw可能不是标准的Linux内存映射标志，可能是特定于工具或版本的。
7ffd2ac21000-7ffd2acc7000 rw-p 00000000 00:00 0 [stack]
这是一个内存映射的地址范围和属性。
7ffd2ac21000-7ffd2acc7000：内存映射的起始和结束地址。
rw-p：权限和类型。r表示可读，w表示可写，-表示不可执行，p表示私有。
00000000：文件偏移量（对于堆栈来说，这通常是0，因为堆栈不是映射自文件的）。
00:00 0：设备号和inode号（对于堆栈来说，这些通常是0，因为堆栈不是通过文件系统设备创建的）。
[stack]：该内存映射的注释，表明这是堆栈内存。
Size: 664 kB
该内存映射的总大小。
KernelPageSize: 4 kB
MMUPageSize: 4 kB
内核页面大小和MMU页面大小，通常这两个值相同，并且与系统页面大小相匹配。
Rss: 664 kB
Pss: 664 kB
Pss_Dirty: 664 kB
Rss：当前驻留在物理内存中的页面大小。
Pss：按比例设置的大小，考虑了共享内存的情况。
Pss_Dirty：脏页的Pss值（在这个例子中，由于所有页面都是私有的且全部被修改，所以与Rss相同）。
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 664 kB
这些行显示了干净和脏页面的共享和私有部分的大小。在这个例子中，所有页面都是私有的且都是脏的（即已被修改）。
Referenced: 664 kB
自上次内存报告以来被访问过的页面大小。
Anonymous: 664 kB
没有映射到任何文件的内存区域（如堆内存或堆栈）的大小。
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
这些行涉及更高级的内存管理技术，如内核同页合并（KSM）、懒释放、大页内存（AnonHugePages）、PMD映射等。在这个例子中，它们都没有被使用。
Swap: 0 kB
SwapPss: 0 kB
交换到磁盘的页面大小和按比例设置的交换大小。在这个例子中，没有页面被交换。
Locked: 0 kB
被锁定的内存量。在这个例子中，没有内存被锁定。
THPeligible: 0
这可能表示该内存区域是否符合透明大页（THP）的资格。0表示不符合或THP未启用。不过，请注意，这个字段的确切含义可能取决于您的系统和工具版本。
分析结果以及重点关注
根据以上的分析，我们这里重点关注
7ffd2ac21000-7ffd2acc7000 rw-p 00000000 00:00 0 [stack]
Rss: 664 kB
RSS 表示实际占用物理内存大小
这个例子中体现出来：
该进程占用 stack 664KB。
这个例子我最终分析出来的结果是：
这里的demo 是 SubscribeHelloWorldClient。
