What is causing "Unable to allocate memory for pool" in PHP?

Question

I've occasionally run up against a server's memory allocation limit, particularly with a bloated application like Wordpress, but never encountered "Unable to allocate memory for pool" and having trouble tracking down any information. Does anyone know what this means? I've tried increasing the `memory_limit` without success. I also haven't made any significant changes to the application. One day there was no problem, the next day I hit this error.

Accepted Answer

Probably is APC related.

For the people having this problem, please specify you .ini settings. Specifically your apc.mmap_file_mask setting.

For file-backed mmap, it should be set to something like:

```
apc.mmap_file_mask=/tmp/apc.XXXXXX
```

To mmap directly from /dev/zero, use:

```
apc.mmap_file_mask=/dev/zero
```

For POSIX-compliant shared-memory-backed mmap, use:

```
apc.mmap_file_mask=/apc.shm.XXXXXX
```

What is causing "Unable to allocate memory for pool" in PHP?

Solution

Problem