[英]How to share mmap between python and node processes
I'm trying to share memory between a python process and a nodejs process started from the python process using an anonymous mmap.我正在尝试使用匿名 mmap 在 python 进程和从 python 进程启动的 nodejs 进程之间共享内存。 Essentially, the python process begins, initializes the mmap and starts a subprocess using either call or Popen to launch a child that runs some node code.
本质上,python 进程开始,初始化 mmap 并使用 call 或 Popen 启动子进程以启动运行某些节点代码的子进程。 This nodejs code uses mmap to try to access the same area in memory.
此 nodejs 代码使用 mmap 尝试访问内存中的相同区域。 However I get two different mappings and no data is shared between them.
但是我得到了两个不同的映射,并且它们之间没有共享数据。 Why is this?
为什么是这样?
import mmap, math, os
from subprocess import call
mm = mmap.mmap( -1, 1024,
flags=mmap.MAP_SHARED | mmap.MAP_ANONYMOUS,
prot= mmap.PROT_READ | mmap.PROT_WRITE )
mm.seek(0)
mm.write('hello world!\n'.encode('utf-8'))
call([
'node', '-e',
"""
const mmap = require('mmap.js');
const fileBuf = mmap.alloc(
1024,
mmap.PROT_READ | mmap.PROT_WRITE,
mmap.MAP_SHARED| mmap.MAP_ANONYMOUS,
-1,
0
)
console.log(fileBuf.toString('utf-8'));
"""
])
The mmap.js that I am using is a NAPI of the original mmap c function.我使用的 mmap.js 是原始 mmap c 函数的 NAPI。 This is the github for this library.
这是这个库的github。
EDIT:编辑:
Thanks to 'that other guy' for his answer.感谢“那个其他人”的回答。 It was the correct one.
这是正确的。 Here's some sample code that works out of the box!: test_mmap.py
这是一些开箱即用的示例代码!:test_mmap.py
import os, ctypes, posix_ipc, sys, mmap
from subprocess import call
SHARED_MEMORY_NAME = "/shared_memory"
memory = posix_ipc.SharedMemory(SHARED_MEMORY_NAME, posix_ipc.O_CREX,
size=1024)
mapFile = mmap.mmap(memory.fd, memory.size)
memory.close_fd()
mapFile.seek(0)
mapFile.write("Hello world!\n".encode('utf-8'))
mapFile.seek(0)
print("FROM PYTHON MAIN PROCESS: ", mapFile.readline().decode('utf-8'))
mapFile.seek(0)
call([
"node", "./test_mmap.js", SHARED_MEMORY_NAME
])
mapFile.close()
posix_ipc.unlink_shared_memory(SHARED_MEMORY_NAME)
test_mmap.js test_mmap.js
const args = process.argv;
const mmap = require('mmap.js');
const shm = require('nodeshm');
const SHM_FILE_NAME=args[args.length-1];
let fd = shm.shm_open(SHM_FILE_NAME, shm.O_RDWR, 0600);
if (fd == -1){
console.log("FD COULD NOT BE OPENED!");
throw "here";
}
let mm = mmap.alloc(1024, mmap.PROT_READ | mmap.PROT_WRITE, mmap.MAP_SHARED, fd, 0);
console.log("FROM NODE: ", mm.slice(0, mm.indexOf('\n')).toString('utf-8'));
Sample output:示例输出:
FROM PYTHON MAIN PROCESS: Hello world!
FROM NODE: Hello world!
Fortunately this doesn't work: imagine how confusing if all of the system's MAP_ANONYMOUS
mappings were against the same area and kept overwriting each other.幸运的是,这行不通:想象一下,如果系统的所有
MAP_ANONYMOUS
映射都针对同一区域并不断相互覆盖,那该有多混乱。
Instead, use shm_open
to create a new handle you can mmap in both processes.相反,使用
shm_open
创建一个新句柄,您可以在两个进程中进行映射。 This is a portable wrapper around the equally valid but less portable strategy of creating and mmap'ing a file in /dev/shm/
.这是围绕在
/dev/shm/
中创建和映射文件的同样有效但便携性较低的策略的便携包装器。
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