Liveboot内存扩容求助：Ubuntu 16.04.3 LTS系统卡顿问题

Hey Doug, let's break down why your RAM-disk LXDE live setup is stuttering—especially that annoying external keyboard lag. Given your 16GB RAM laptop, this shouldn't be happening, so let's dig into the most likely culprits and fixes:

1. First: Verify RAM Disk & System Memory Usage #

Since you're loading programs/configs into a RAM disk, the #1 suspect is that your RAM disk is running out of space, forcing the system to thrash memory (even without swap). Here's how to check:

• Run free -h to see total RAM, used space, cached/buffered memory, and free space. If free RAM is under ~2GB, that's a red flag.
• Get the full df -h output (your snippet cut off) and look for your RAM disk (it might show as tmpfs or a /dev/loop device). Check its Use%—if it's above 90%, that's almost certainly causing the stutter.
• Use htop to visualize real-time memory usage, sorted by MEM%—you'll quickly spot if any process is hogging RAM or the RAM disk.

2. Troubleshoot External Keyboard Lag #

Keyboard lag often ties into system-wide IO or CPU bottlenecks, not just the keyboard itself:

• Run iostat -x 1 to monitor disk activity. If your mounted HDD at /media/ubuntu/ shows high %util (over 80%), that means the disk is being hammered—any process writing/reading there will slow down the entire system, including input handling.
• Check for runaway processes with top (sort by %CPU or %IO). Look for things like loggers, sync daemons, or even a misbehaving app constantly writing to the HDD.
• Test raw input with xinput list to find your external keyboard's device ID, then run xinput test <device-id>. If you see delayed or missing keystrokes here, it might be a driver issue (more on that below).

3. Tweak RAM Disk Configuration #

If your RAM disk is too small, adjust its size in your boot script—you've got plenty of RAM to spare:

• Locate the part of your boot script that creates the RAM disk (usually a mount -t tmpfs command). Increase the size parameter, e.g., mount -t tmpfs -o size=10G tmpfs /path/to/your/ramdisk. Leave ~4-6GB of RAM free for the OS and background processes.
• Move non-critical files off the RAM disk: Things like log directories, browser caches, or temporary files can live on your /media/ubuntu/ HDD instead. This frees up RAM disk space and reduces unnecessary writes.

4. Trim Down LXDE & System Services #

Even LXDE can bloat up in a live environment—disable what you don't need:

• Run systemctl list-unit-files --state=enabled to see active services. Disable ones you don't use (e.g., bluetooth, cups for printing, avahi-daemon for network discovery) with sudo systemctl disable <service-name>.
• Open lxsession-default-apps and go to the "Autostart" tab—uncheck any apps that launch automatically but aren't essential (like a file manager that auto-mounts drives, or desktop widgets).

5. Check for Kernel/Driver Issues #

Ubuntu 16.04 is pretty old, so outdated drivers might be causing input lag:

• Run uname -r to check your kernel version. Consider upgrading to the latest HWE kernel for 16.04 (it's backported from newer releases) with sudo apt install linux-generic-hwe-16.04.
• Check system logs for keyboard-related errors with dmesg | grep -i input or dmesg | grep -i keyboard. Look for lines about "failed to initialize" or "input device disconnected"—these point to driver conflicts.

Start with the RAM disk check first—that's the most probable fix here. Let me know what your free -h and full df -h outputs show if you need more help!

内容的提问来源于stack exchange，提问作者Doug