Here's the related configuration:

proxy_cache_path /var/www/cache levels=1:2 keys_zone=kendi-cache:1000m max_size=10000m;
proxy_cache_key "$request_uri|$request_body";


When I send small requests, nginx works great.
When I send a large post request (long uri) I get these logs:

I have debug on error.log, here's the output:

2013/01/08 13:50:25 [error] 32765#0: *1 cache key too large, increase upstream buffer size 4096, client:...
2013/01/08 13:51:01 [warn] 32765#0: *1 an upstream response is buffered to a temporary file /var/www/cache/tmp/0000000001 while reading upstream, client:...
2013/01/08 13:51:20 [notice] 300#0: http file cache: /var/www/cache 0.000M, bsize: 4096
2013/01/08 13:51:20 [notice] 32764#0: signal 17 (SIGCHLD) received
2013/01/08 13:51:20 [notice] 32764#0: cache loader process 300 exited with code 0
2013/01/08 13:51:20 [notice] 32764#0: signal 29 (SIGIO) received

I'm not sure what to do here.