Memfd is a wrapper around the memfd_create system call which creates an anonymous memory-backed file and returns a file descriptor reference to it. It provides a simple alternative to manually mounting a tmpfs filesystem and creating and opening a file in that filesystem. The file is a regular file on a kernel-internal filesystem and thus supports most operations such as ftruncate(2), read(2), dup(2), mmap(2) etc.
Imagine that malloc(3) returns a file descriptor instead of a pointer. The system call also introduced a new feature called "file sealing". With file sealing you can specify to the kernel that the file backed by anonymous memory has certain restrictions such as: no writes occur to the file, and the file size does not shrink or grow. For IPC based servers the F_SEAL_SHRINK seal is of interest and the server can be sure clients won't shrink it's buffers and can read files without side effects of unexpected shrinking.
- Shared memory buffers don't require a mount point or having to create files on the filesystem soley to use as shared memory.
- An alternative to creating files in
/tmpif there's never an intention to actually link the file in the filesystem. - Zero-copy transfer of large objects through IPC: one process creates a shared memory object and just passes the file descriptor to a remote process.
- Preventing specific operations on a file through the file sealing API.
- Better server stability and less risk of unexpected SIGBUS due to unexpected client buffer alterations.
Linux ONLY!
gem install memfd
TODO
#! /usr/bin/env ruby
require 'memfd'-
Ruby 2.1.0 or higher, including any development packages necessary to compile native extensions.
-
A Linux Kernel version > 3.17
bundle install
bundle exec rakeMIT. See the LICENSE.txt file.
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent