Menu
I have scripts that make hundreds of quick succession, small, temp files needing to be created and very soon read back in, then unlinked.
My testing shows little if any performance difference by putting said files in /tmp (to disk) or into /dev/shm (filesystem-level shared memory) on Linux even under moderate load. I attribute this to the filesystem cache.
Granted the disk will eventually get hit with the fileystem actions, but on multiple small write-read temp files, why would you (not) recommend /dev/shm over disk-backed directory? Have you noticed big performance increases with shared memory directory over a cached VFS?
964
/dev/shm is a temporary file storage filesystem (see tmpfs ) that uses RAM for the storage. It can function as shared memory that facilitates IPC. It is a world-writeable directory. The size of /dev/shm is limited by excess RAM on the system, and hence you're more likely to run out of space on this filesystem.
shm / shmfs is also known as tmpfs, which is a common name for a temporary file storage facility on many Unix-like operating systems. It is intended to appear as a mounted file system, but one which uses virtual memory instead of a persistent storage device.
Temporary files on Linux have traditionally been written to /tmp, at least those that don't need to persist across boots. Several Linux distributions are now planning to mount /tmp as a RAM-based tmpfs by default, which should generally be an improvement in a wide variety of scenarios—but not all.
Note the /dev/shm partition now has 3 GB of space available.
/dev/shm is intended for a very special purpose, not for files to be put to by arbitrary programs.
In contrast, /tmp is exactly made for this. On my systems, /tmp is a tmpfs as well, in contrast to /var/tmp which is designed for putting larger files, potentially staying longer.
98
It is essentially the same (shm is also backed implicitly by the disk when you have a swapfile).
/tmp has the advantage that it fills up harder (considering your hard disk is likely larger than your swapfile). And also it is more widely supported.
32
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
