Wi-Fi Issues
In Yosemite, Macs are using Bonjour over Apple Wireless Direct Link (AWDL) to discover devices to connect to for AirDrop, AirPlay, and other services. AWDL is a low-latency, high-throughput, peer-to-peer connection that runs over Wi-Fi but has its own dedicated network interface (much like general Wi-Fi or Ethernet). In the past, Bonjour was used only over standard Wi-Fi networks or Bluetooth. But when it works over AWDL, it appears to strain the hardware, hurting performance.
Fortunately, it’s easy to disable AWDL, but the fix also disables AirDrop and requires working at the command line. Copy the line below and, at the command line in Terminal, paste it, press Return, and enter your password. (Unfortunately, it doesn’t persist between reboots, so you’ll have to apply the fix every time you reboot your Mac.)
sudo ifconfig awdl0 down
If you see the error message “ifconfig: interface awdl0 does not exist,” you have older hardware that doesn’t support AWDL.
You can re-enable AWDL and AirDrop without rebooting by entering this line in the Terminal.
sudo ifconfig awdl0 up
Save Dialogs Expand Offscreen
Have you ever tried to save a document, only to find that you can’t see the Save button because it’s off the screen? A bug in Yosemite can apparently make Save dialogs grow in height by 22 pixels each time one is opened.
Hold the Shift key down, hover over the left or right edge of the dialog until the cursor becomes opposing arrows, and then drag inward to shrink the Save dialog.