# Mouse Polling Rate

If you have invested in a high resolution mouse, adjusting the USB polling rate is a common trick to utilise the added precision it brings. The polling rate (or report rate) determines how often the mouse sends information to your computer. Measured in Hertz (Hz), this setting equates to lag time (in ms).

By default, the USB polling rate is set at 125 Hz. The table below represents combinations of Hz values and their corresponding delay time:

Hz | ms
--- | ---
1000 | 1
500 | 2
250 | 4
125 | 8
100 | 10

If the polling rate is set at 125 Hz, the mouse cursor can only be updated every 8 milliseconds. In situations where lag is critical (for example games), it is useful to decrease this value to as little as possible. Increasing the polling interval will improve precision at the tradeoff of using more CPU resources, therefore care should be taken when adjusting this value.

## Setting the polling rate

Here we are using the `usbhid` module of the kernel to set a custom "mousepoll" rate. Simply add the following line to your `/etc/modprobe.d/modprobe.conf` file:

    options usbhid mousepoll=[polling interval]

(where [polling interval] is a number in ms from the table above. For example, to set a polling rate of 500Hz:

    options usbhid mousepoll=2

To change the polling rate without rebooting

    modprobe -r usbhid && modprobe usbhid

Warning: Make sure that both commands execute otherwise you will be unable to use the mouse and keyboard and will have to reboot or ssh into your machine.

Then unplug and replug your mouse.

Note: If you use the usbinput and udev hooks in your initramfs, usbhid will included on the image and you'll need to add `/etc/modprobe.d/modprobe.conf` to the FILES entry in `/etc/mkinitcpio.conf`. Remember to regenerate your image after changing the config. Without doing this, the module will be inserted during early userspace without the polling option. Alternatively, you can add usbhid.mousepoll=X to your kernel command line.

## Displaying current mouse rate

A tool exists (named evhz) that can display the current mouse refresh rate -- useful when checking that your customized polling settings have been applied.

evhz.c

Compile it with:

    gcc -o evhz evhz.c

Then execute as root:

    ./evhz

Alternatively, Windows tools such as DirectX mouserate checker can be run using WINE.

## Further Reading

- CS:S Mouse Optimization Guide -- largely aimed at Windows users, though the same principles apply for Linux.

Category:

- Mice