inotify watch 耗尽

每个 linux 进程可以持有多个 fd,每个 inotify 类型的 fd 可以 watch 多个目录,每个用户下所有进程 inotify 类型的 fd 可以 watch 的总目录数有个最大限制,这个限制可以通过内核参数配置: fs.inotify.max_user_watches

查看最大 inotify watch 数:

$ cat /proc/sys/fs/inotify/max_user_watches
8192

使用下面的脚本查看当前有 inotify watch 类型 fd 的进程以及每个 fd watch 的目录数量,降序输出,带总数统计:

#!/usr/bin/env bash
#
# Copyright 2019 (c) roc
#
# This script shows processes holding the inotify fd, alone with HOW MANY directories each inotify fd watches(0 will be ignored).
total=0
result="EXE PID FD-INFO INOTIFY-WATCHES\n"
while read pid fd; do \
exe="$(readlink -f /proc/$pid/exe || echo n/a)"; \
fdinfo="/proc/$pid/fdinfo/$fd" ; \
count="$(grep -c inotify "$fdinfo" || true)"; \
if [ $((count)) != 0 ]; then
total=$((total+count)); \
result+="$exe $pid $fdinfo $count\n"; \
fi
done <<< "$(lsof +c 0 -n -P -u root|awk '/inotify$/ { gsub(/[urw]$/,"",$4); print $2" "$4 }')" && echo "total $total inotify watches" && result="$(echo -e $result|column -t)\n" && echo -e "$result" | head -1 && echo -e "$result" | sed "1d" | sort -k 4rn;

示例输出:

total 7882 inotify watches
EXE PID FD-INFO INOTIFY-WATCHES
/usr/local/qcloud/YunJing/YDEyes/YDService 25813 /proc/25813/fdinfo/8 7077
/usr/bin/kubelet 1173 /proc/1173/fdinfo/22 665
/usr/bin/ruby2.3 13381 /proc/13381/fdinfo/14 54
/usr/lib/policykit-1/polkitd 1458 /proc/1458/fdinfo/9 14
/lib/systemd/systemd-udevd 450 /proc/450/fdinfo/9 13
/usr/sbin/nscd 7935 /proc/7935/fdinfo/3 6
/usr/bin/kubelet 1173 /proc/1173/fdinfo/28 5
/lib/systemd/systemd 1 /proc/1/fdinfo/17 4
/lib/systemd/systemd 1 /proc/1/fdinfo/18 4
/lib/systemd/systemd 1 /proc/1/fdinfo/26 4
/lib/systemd/systemd 1 /proc/1/fdinfo/28 4
/usr/lib/policykit-1/polkitd 1458 /proc/1458/fdinfo/8 4
/usr/local/bin/sidecar-injector 4751 /proc/4751/fdinfo/3 3
/usr/lib/accountsservice/accounts-daemon 1178 /proc/1178/fdinfo/7 2
/usr/local/bin/galley 8228 /proc/8228/fdinfo/10 2
/usr/local/bin/galley 8228 /proc/8228/fdinfo/9 2
/lib/systemd/systemd 1 /proc/1/fdinfo/11 1
/sbin/agetty 1437 /proc/1437/fdinfo/4 1
/sbin/agetty 1440 /proc/1440/fdinfo/4 1
/usr/bin/kubelet 1173 /proc/1173/fdinfo/10 1
/usr/local/bin/envoy 4859 /proc/4859/fdinfo/5 1
/usr/local/bin/envoy 5427 /proc/5427/fdinfo/5 1
/usr/local/bin/envoy 6058 /proc/6058/fdinfo/3 1
/usr/local/bin/envoy 6893 /proc/6893/fdinfo/3 1
/usr/local/bin/envoy 6950 /proc/6950/fdinfo/3 1
/usr/local/bin/galley 8228 /proc/8228/fdinfo/3 1
/usr/local/bin/pilot-agent 3819 /proc/3819/fdinfo/5 1
/usr/local/bin/pilot-agent 4244 /proc/4244/fdinfo/5 1
/usr/local/bin/pilot-agent 5901 /proc/5901/fdinfo/3 1
/usr/local/bin/pilot-agent 6789 /proc/6789/fdinfo/3 1
/usr/local/bin/pilot-agent 6808 /proc/6808/fdinfo/3 1
/usr/local/bin/pilot-discovery 6231 /proc/6231/fdinfo/3 1
/usr/local/bin/sidecar-injector 4751 /proc/4751/fdinfo/5 1
/usr/sbin/acpid 1166 /proc/1166/fdinfo/6 1
/usr/sbin/dnsmasq 7572 /proc/7572/fdinfo/8 1

如果看到总 watch 数比较大,接近最大限制,可以修改内核参数调高下这个限制。

临时调整:

sudo sysctl fs.inotify.max_user_watches=524288

永久生效:

echo "fs.inotify.max_user_watches=524288" >> /etc/sysctl.conf && sysctl -p

打开 inotify_add_watch 跟踪,进一步 debug inotify watch 耗尽的原因:

echo 1 >> /sys/kernel/debug/tracing/events/syscalls/sys_exit_inotify_add_watch/enable