在Linux中，如何查找分叉进程与写时复制之间共享多少内存? [英] How to find how much memory is shared between forked process with copy-on-write in Linux?
问题描述
如果有一个进程读取一个大文件并将其保存在其内存中(或只是一个malloc分配的char *)，并且该主进程是分叉的，则子进程仅从该内存(或char *)中读取，根据写入时复制，不会复制保存指针的内存，并且父级和子级都共享相同的内存，直到它们中的任何一个试图在该内存上进行写时为止，在这种情况下，进程将复制该内存.记忆并改变它.
If there is a process that reads a big file and saves it in its memory(or just a malloced char*), and that main process is forked, if the child process only reads from that memory(or the char*), according to copy-on-write, the memory where the pointer is saved is not copied, and both parent and child share the same memory until either one of them tries to write on that memory in which case the process makes a copy of the memory and changes that.
所以我的问题是，是否实现了复制写入，是否有办法知道子进程使用的与主进程不共享的内存量? 换句话说，如果子进程使用某些读取调用中的父级内存，则该子进程实际使用了多少内存?
So my question is if there is a copy-on write implemented, is there a way to know the amount of memory that the child uses that is not shared with the main process? In other words how much memory does a child process actually use, if it uses parents memory from some read calls?
top或ps命令将仅给出子级应该具有的内存总量. (即假设内存或指针中的数据是孩子复制的.)
top, or ps commands will only give the total amount of memory that the child is supposed to have. (i.e assuming that data in memory or pointer is copied by the child.)
有没有一种方法可以获取CoW语义实际使用的数据量?
Is there a way to get the amount of data that is actually used by CoW semantics?
我按照aix和Mat的建议进行了/proc/[pid]/smaps操作，但是我发现的只是很多空的smaps文件.我尝试使用此命令来查找哪些文件中包含数据:tail -n 5 */smaps | less
我得到的o/p是
I went through /proc/[pid]/smaps as suggested by aix and Mat, but all i found was lots of empty smaps files. I tried this command to find which files has data in them: tail -n 5 */smaps | less
And the o/p that i got was
==> 1012/smaps <==
==> 1074/smaps <==
==> 10/smaps <==
==> 1148/smaps <==
==> 11862/smaps <==
==> 11/smaps <==
==> 1355/smaps <==
==> 1356/smaps <==
==> 1357/smaps <==
==> 1358/smaps <==
==> 1361/smaps <==
==> 13/smaps <==
==> 14900/smaps <==
==> 14/smaps <==
==> 1501/smaps <==
==> 15/smaps <==
==> 1684/smaps <==
==> 1685/smaps <==
==> 16/smaps <==
==> 17772/smaps <==
==> 17827/smaps <==
==> 17/smaps <==
==> 18490/smaps <==
==> 18/smaps <==
==> 1932/smaps <==
==> 1934/smaps <==
==> 19863/smaps <==
==> 19/smaps <==
==> 1/smaps <==
==> 20125/smaps <==
==> 20126/smaps <==
==> 20127/smaps <==
==> 20128/smaps <==
==> 20129/smaps <==
==> 20134/smaps <==
==> 20135/smaps <==
==> 20811/smaps <==
==> 20868/smaps <==
==> 20/smaps <==
==> 21116/smaps <==
==> 21774/smaps <==
==> 21/smaps <==
==> 22393/smaps <==
==> 22394/smaps <==
==> 22395/smaps <==
==> 22398/smaps <==
==> 22639/smaps <==
==> 22824/smaps <==
==> 22/smaps <==
==> 23009/smaps <==
==> 23058/smaps <==
==> 23059/smaps <==
Private_Dirty: 0 kB
Referenced: 0 kB
Swap: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
==> 23835/smaps <==
==> 23961/smaps <==
==> 23962/smaps <==
==> 23963/smaps <==
==> 23964/smaps <==
==> 23/smaps <==
==> 24180/smaps <==
==> 24268/smaps <==
==> 24467/smaps <==
==> 24/smaps <==
==> 252/smaps <==
==> 25352/smaps <==
==> 25435/smaps <==
==> 25/smaps <==
==> 26465/smaps <==
==> 26/smaps <==
==> 27884/smaps <==
==> 27/smaps <==
==> 28/smaps <==
==> 29/smaps <==
==> 2/smaps <==
==> 303/smaps <==
==> 30/smaps <==
==> 316/smaps <==
==> 31/smaps <==
==> 32074/smaps <==
==> 32076/smaps <==
==> 32112/smaps <==
Private_Dirty: 0 kB
Referenced: 0 kB
Swap: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
==> 32116/smaps <==
Private_Dirty: 0 kB
Referenced: 0 kB
Swap: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
==> 322/smaps <==
==> 32466/smaps <==
==> 32467/smaps <==
==> 32/smaps <==
==> 33/smaps <==
==> 34/smaps <==
==> 37/smaps <==
==> 38/smaps <==
==> 3991/smaps <==
==> 3992/smaps <==
==> 39/smaps <==
==> 3/smaps <==
==> 4005/smaps <==
==> 4006/smaps <==
==> 4007/smaps <==
==> 4008/smaps <==
==> 4009/smaps <==
==> 4010/smaps <==
==> 4018/smaps <==
==> 4029/smaps <==
==> 4038/smaps <==
==> 4044/smaps <==
==> 4045/smaps <==
==> 4046/smaps <==
==> 4053/smaps <==
==> 4054/smaps <==
==> 4055/smaps <==
==> 40/smaps <==
==> 41/smaps <==
==> 42/smaps <==
==> 4339/smaps <==
==> 435/smaps <==
==> 436/smaps <==
==> 43/smaps <==
==> 44/smaps <==
==> 45/smaps <==
==> 46/smaps <==
==> 47/smaps <==
==> 48/smaps <==
==> 49/smaps <==
==> 4/smaps <==
==> 50/smaps <==
==> 51/smaps <==
==> 52/smaps <==
==> 53/smaps <==
==> 54/smaps <==
==> 55/smaps <==
==> 56/smaps <==
==> 57/smaps <==
==> 58/smaps <==
==> 5988/smaps <==
==> 59/smaps <==
==> 5/smaps <==
==> 6058/smaps <==
==> 6059/smaps <==
Private_Dirty: 0 kB
Referenced: 0 kB
Swap: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
==> 60/smaps <==
==> 61/smaps <==
==> 62/smaps <==
==> 63/smaps <==
==> 64/smaps <==
==> 65/smaps <==
==> 66/smaps <==
==> 67/smaps <==
==> 68/smaps <==
==> 69/smaps <==
==> 6/smaps <==
==> 70/smaps <==
==> 71/smaps <==
==> 72/smaps <==
==> 73/smaps <==
==> 74/smaps <==
==> 771/smaps <==
==> 77/smaps <==
==> 782/smaps <==
==> 78/smaps <==
==> 79/smaps <==
==> 7/smaps <==
==> 80/smaps <==
==> 814/smaps <==
==> 819/smaps <==
==> 81/smaps <==
==> 82/smaps <==
==> 83/smaps <==
==> 84/smaps <==
==> 8654/smaps <==
==> 8655/smaps <==
==> 8656/smaps <==
==> 892/smaps <==
==> 8/smaps <==
==> 949/smaps <==
==> 950/smaps <==
==> 9/smaps <==
==> self/smaps <==
Private_Dirty: 0 kB
Referenced: 0 kB
Swap: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
那我现在该怎么办?我有正在运行的空白smap的进程.我如何获取那些pid的图?
So what am i supposed to do now? I have processes that have blank smaps that are running. How do i get the smaps of those pid's?
推荐答案
我不知道会为您提供此信息的工具，但您可能可以根据/proc/[pid]/smaps进行计算:
I don't know of a tool that would give you this information, but you can probably compute this based on /proc/[pid]/smaps:
/proc/[pid]/smaps (since Linux 2.6.14)
This file shows memory consumption for each of the process’s mappings.
For each of mappings there is a series of lines such as the following:
08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
Size: 464 kB
Rss: 424 kB
Shared_Clean: 424 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
The first of these lines shows the same information as is displayed for
the mapping in /proc/[pid]/maps. The remaining lines show the size of
the mapping, the amount of the mapping that is currently resident in RAM,
the number of clean and dirty shared pages in the mapping, and the number
of clean and dirty private pages in the mapping.
有关详细信息，请参见获得/proc/pid/smaps 中有关进程的内存使用情况的信息.
For details, see Getting information about a process' memory usage from /proc/pid/smaps.
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