Using ramdisks with Cargo
I have a bit of a history of killing SSDs - probably because I do a bit too much compiling and management of thousands of tiny files. Plenty of developers have this problem! So while thinking one evening, I was curious if I could setup a ramdisk on my mac for my cargo work to output to.
Making the ramdisk
On Linux you'll need to use tmpfs or some access to /dev/shm.
On OSX you need to run a script like the following:
diskutil partitionDisk $(hdiutil attach -nomount ram://4096000) 1 GPTFormat APFS 'ramdisk' '100%'
This creates and mounts a 4GB ramdisk to /Volumes/ramdisk. Make sure you have enough ram!
Asking cargo to use it
We probably don't want to make our changes permant in Cargo.toml, so we'll use the environment:
CARGO_TARGET_DIR=/Volumes/ramdisk/rs cargo ...
Does it work?
Disk Build (SSD, 2018MBP)
Finished dev [unoptimized + debuginfo] target(s) in 2m 29s
4 GB APFS ramdisk
Finished dev [unoptimized + debuginfo] target(s) in 1m 53s
For me it's more valuable to try and save those precious SSD write cycles, so I think I'll try to stick with this setup. You can see how much rust writes by doing a clean + build. My project used the following:
Filesystem Size Used Avail Capacity iused ifree %iused Mounted on /dev/disk110s1 2.0Gi 1.2Gi 751Mi 63% 3910 9223372036854771897 0% /Volumes/ramdisk
Make it permanent
Put the following in /Library/LaunchDaemons/au.net.blackhats.fy.ramdisk.plist
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0"> <dict> <key>Label</key> <string>au.net.blackhats.fy.ramdisk</string> <key>Program</key> <string>/usr/local/libexec/ramdisk.sh</string> <key>RunAtLoad</key> <true/> <key>StandardOutPath</key> <string>/var/log/ramdisk.log</string> </dict> </plist>
And the following into /usr/local/libexec/ramdisk.sh
#!/bin/bash date diskutil partitionDisk $(hdiutil attach -nomount ram://4096000) 1 GPTFormat APFS 'ramdisk' '100%'
Finally put this in your cargo file of choice
[build] target-dir = "/Volumes/ramdisk/rs"
Future william will need to work out if there are negative consequences to multiple cargo projects sharing the same target directory ... hope not!
# Init the service launchctl load /Library/LaunchDaemons/au.net.blackhats.fy.ramdisk.plist