Linux 上 AI Agent 默认会吃光你的内存

My 64 GB Linux workstation kept freezing while coding agents worked on a couple of projects. All 4 GB of swap filled up. Applications were killed. Half the memory looked like cache. Then I found 22 GB of agent-created files in a tmpfs-backed /tmp. Not all cache is disposable tmpfs stores file contents in RAM or swap. Unlike clean disk-backed cache, those contents cannot simply be discarded. Some memory monitors include tmpfs in cache-related accounting, making the memory pressure easy to misread.1 Memory-backed temporary storage can offer fast I/O, fewer storage writes, and cleanup on reboot. But swapping can undermine those benefits.2 The distinction is workload size. Systemd recommends /tmp for small, bounded files and /var/tmp for larger data.3 This is not uniquely an AI problem: GCC also creates temporary intermediate files.4 Parallel agent work simply made the trade-off visible on my machine. Check your machine Run these in a Linux terminal: # Filesystem containing /tmp findmnt -T /tmp -o TARGET,SOURCE,FSTYPE # Capacity and usage of that filesystem df -hT /tmp # Directory sizes, largest last; stay on one filesystem sudo du -x -h --max-depth=1 /tmp | sort -h # RAM and swap usage free -h Enter fullscreen mode Exit fullscreen mode Look for tmpfs under FSTYPE. Keep -T: plain findmnt /tmp can return nothing when /tmp is not a separate mount.5 df measures the containing filesystem; du measures the directory tree.67 In free, focus on available.8 Large tmpfs usage alongside low available memory deserves investigation—not automatic blame for every crash. Option 1: redirect heavy workloads Create a private directory and check its filesystem and free space: mkdir -p "$HOME/.local/tmp" chmod 700 "$HOME/.local/tmp" findmnt -T "$HOME/.local/tmp" -o TARGET,SOURCE,FSTYPE df -hT "$HOME/.local/tmp" Enter fullscreen mode Exit fullscreen mode mkdir -p creates missing directories; chmod 700 restricts ordinary access to the owner.910 Confirm the directory is disk-backed before proceeding. export TMPDIR="$HOME/.local/tmp" Enter fullscreen mode Exit fullscreen mode Launch your agent from that same terminal. Programs honoring TMPDIR can use the new location. Hard-coded /tmp paths and existing workspaces need separate changes.3 Verify the path and filesystem inside the agent’s actual execution environment, especially with containers or sandboxes.5 Clean up completed scratch data yourself; this directory does not inherit /tmp’s cleanup policy.3 Option 2: make /tmp disk-backed system-wide For systemd-based distributions, inspect first: # Mount unit and any overrides systemctl cat tmp.mount --no-pager # Explicit /tmp configuration; no output means no matching entry findmnt --fstab --mountpoint /tmp # Root filesystem, mount options, and free space findmnt -T / -o TARGET,SOURCE,FSTYPE,OPTIONS df -hT / Enter fullscreen mode Exit fullscreen mode tmp.mount is one name, with a dot.11 Use the following only when /tmp is tmpfs, its unit is distribution-provided with no local customizations, /etc/fstab has no /tmp entry, and / is writable, disk-backed, and has adequate space. Otherwise, use Option 1 rather than forcing this shortcut.511 sudo systemctl mask tmp.mount Enter fullscreen mode Exit fullscreen mode This prevents future activation without unmounting the current /tmp.11 Save your work, copy anything needed out of /tmp, then reboot when ready. Existing tmpfs files disappear; they do not migrate to disk.1 After reboot, verify: findmnt -T /tmp -o TARGET,SOURCE,FSTYPE Enter fullscreen mode Exit fullscreen mode /tmp should now belong to the disk-backed root filesystem. To reverse the mask, run sudo systemctl unmask tmp.mount, then reboot.11 This trades memory-backed storage for root-disk usage and can remove mount-specific restrictions such as nosuid,nodev. Disk space, cleanup, and security policy still matter.123 Why macOS and Windows usually avoid this trap Native macOS and Windows normally use disk-backed temporary directories, so large temporary trees primarily consume disk space.1314 They can still exhaust memory; disk-backed does not mean cache-free.15 For Linux containers or virtual machines, check inside that environment.5 The takeaway This is not a reason to disable tmpfs everywhere. It is a reason to put multi-gigabyte workspaces on storage chosen deliberately. “Temporary” describes how long data is needed—not where it belongs. Linux kernel: Tmpfs. ↩ Ubuntu: Data Driven Analysis — /tmp on tmpfs. ↩ systemd: Using /tmp/ and /var/tmp/ Safely. ↩ GCC: Environment Variables. ↩ findmnt(8). ↩ df(1). ↩ du(1). ↩ free(1). ↩ mkdir(1). ↩ chmod(1). ↩ systemctl(1). ↩ systemd: upstream tmp.mount. ↩ Apple: File System Basics. ↩ Microsoft: GetTempPath2. ↩ Microsoft: File Caching. ↩