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c - Understanding memory maps

问题描述

I'm very new to C programming and investigating continuously increasing RSS size. The suspicion is there is some memory leak. I looked at the /proc/<pid>/maps and found the following:

f8000000-fb180000 rw-p 00000000 00:00 0
fb180000-fd580000 ---p 00000000 00:00 0
fd580000-fdc80000 rw-p 00000000 00:00 0
fdc80000-100000000 ---p 00000000 00:00 0
100000000-1005a0000 rw-p 00000000 00:00 0
1005a0000-140000000 ---p 00000000 00:00 0
7fb45d1dd000-7fb45d1e0000 ---p 00000000 00:00 0
7fb45e0ec000-7fb45e0ef000 ---p 00000000 00:00 0
7fb45e0ef000-7fb45e1ed000 rw-p 00000000 00:00 0
7fb45e1ed000-7fb45e1f0000 ---p 00000000 00:00 0
7fb45e1f0000-7fb45e2ee000 rw-p 00000000 00:00 0
7fb45e2ee000-7fb45e2f1000 ---p 00000000 00:00 0
7fb45e2f1000-7fb45e3ef000 rw-p 00000000 00:00 0
7fb45e3ef000-7fb45e3f2000 ---p 00000000 00:00 0
7fb45e3f2000-7fb45e4f0000 rw-p 00000000 00:00 0
7fb45e4f0000-7fb45e4f3000 ---p 00000000 00:00 0
7fb45e4f3000-7fb45e5f1000 rw-p 00000000 00:00 0
7fb45e5f1000-7fb45e5f4000 ---p 00000000 00:00 0
7fb45e5f4000-7fb45e6f2000 rw-p 00000000 00:00 0
7fb45e6f2000-7fb45e6f5000 ---p 00000000 00:00 0
7fb45e6f5000-7fb45e7f3000 rw-p 00000000 00:00 0
7fb45e7f3000-7fb45e7f6000 ---p 00000000 00:00 0
7fb45e7f6000-7fb45e8f4000 rw-p 00000000 00:00 0
7fb45e8f4000-7fb45e8f7000 ---p 00000000 00:00 0
//Tons of the similar entries...
7fb71652b000-7fb71652c000 rw-p 0001a000 08:01 2187                       /lib/x86_64-linux-gnu/libpthread-2.27.so
7fb716568000-7fb71656f000 r--s 00000000 08:01 5020                       /usr/lib/x86_64-linux-gnu/gconv/gconv-modules.cache
7fb716759000-7fb71675a000 rw-p 00000000 00:00 0
7ffc5f781000-7ffc5f7a2000 rw-p 00000000 00:00 0                          [stack]
7ffc5f7c7000-7ffc5f7ca000 r--p 00000000 00:00 0                          [vvar]
7ffc5f7ca000-7ffc5f7cc000 r-xp 00000000 00:00 0                          [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]

The thing that I noticed was that the vast majority of /proc/<pid>/maps were entries like:

7fb45e7f3000-7fb45e7f6000 ---p 00000000 00:00 0

What does this mean? Doesn't it mean that system allocator release the memory it acquires?

Is there a way to examine the memory content at address, e.g. 7fb45e5f4000-7fb45e6f2000 at run-time?

I tried to attach to the running process with gdb and looked at the memory.

(gdb) x /1xg 0x7fb45e1ed000
0x5e1ed000:     Cannot access memory at address 0x5e1ed000

标签： clinuxmemory-leaks

解决方案

像这样的条目

7fb45e0ec000-7fb45e0ef000 ---p 00000000 00:00 0
7fb45e0ef000-7fb45e1ed000 rw-p 00000000 00:00 0

看起来像线程堆栈及其相关的保护页。

看起来您创建了很多线程，但既没有通过 收获它们，也没有通过pthread_join()分离它们pthread_detach()（或在分离状态下创建它们）。

必须回收非分离线程以将其资源（特别是堆栈）返回给操作系统。

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