correct use of linux inotify - reopen every time?

Question

I'm debugging a system load problem that a customer encounters on their production system and they've made a test application that simulates the load to reproduce the problem: In this particular workload, one of the things the coder did was to: ``` while(1) initialize inotify watch a directory for events receive event process event remove watch close inotify fd ``` Strangely enough, the high system load comes from the `close()` of the inotify fd: ``` inotify_init() = 4 <0.000020> inotify_add_watch(4, "/mnt/tmp/msys_sim/QUEUES/Child_032", IN_CREATE) = 1 <0.059537> write(1, "Child [032] sleeping ", 21) = 21 <0.000012> read(4, "\1\0\0\0\0\1\0\0\0\0\0\0\20\0\0\0SrcFile.b8tlfT\0\0", 512) = 32 <0.231012> inotify_rm_watch(4, 1) = 0 <0.000044> close(4) = 0 <0.702530> open("/mnt/tmp/msys_sim/QUEUES/Child_032", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 4 <0.000031> lseek(4, 0, SEEK_SET) = 0 <0.000010> getdents(4, /* 3 entries */, 32768) = 88 <0.000048> getdents(4, /* 0 entries */, 32768) =…

Accepted Answer

Usually the pseudo code `inotify` loop would look like this:

```
initialize inotify
watch a directory | file for events

while(receive event) {
  process event
}

[ remove watch ]
close inotify fd
```

There is no need to remove the watch and reinitialize inotify on every loop.

correct use of linux inotify - reopen every time?

Solution

Problem