ngx_slab_alloc() failed: no memory in cache keys zone

[Davide D'Amico]

Hi,
I'm setting up a nginx reverse proxy on fbsd 8.1rc2 with this server config:

proxy_cache_path /usr/local/cache/zoneA levels=1:2 keys_zone=IMAGES:10m 
inactive=1h max_size=1g;


After two days of running, I noticed in /var/log/nginx-error.log a lot 
of lines:

2010/07/05 11:46:36 [crit] 85688#0: ngx_slab_alloc() failed: no memory 
in cache keys zone "IMAGES"
2010/07/05 11:46:36 [crit] 85686#0: ngx_slab_alloc() failed: no memory 
in cache keys zone "IMAGES"
2010/07/05 11:46:36 [crit] 85690#0: ngx_slab_alloc() failed: no memory 
in cache keys zone "IMAGES"


Why?

Am I to increase keys_zone size?

I'm reading: http://wiki.nginx.org/NginxHttpProxyModule#proxy_cache_path
but it wasn't useful.

Thanks in advance,
d.