Hello:

Each 10 seconds, the core force expires files until http cache size below 640000 (limits are defined at 2500Mb at config)

grep "cache size" /STORAGE/log.txt
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640339
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640317
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640297
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640262
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640248
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640236
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640226
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640217
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640207
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640197
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640167
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640157
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640141
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640124
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640115
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640057
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 640040
2013/07/18 13:15:22 [debug] 17641#0: http file cache size: 639904
2013/07/18 13:15:32 [debug] 17641#0: http file cache size: 640192
2013/07/18 13:15:32 [debug] 17641#0: http file cache size: 640188
2013/07/18 13:15:32 [debug] 17641#0: http file cache size: 640154
2013/07/18 13:15:32 [debug] 17641#0: http file cache size: 640115
2013/07/18 13:15:32 [debug] 17641#0: http file cache size: 640106
2013/07/18 13:15:32 [debug] 17641#0: http file cache size: 640097
2013/07/18 13:15:32 [debug] 17641#0: http file cache size: 640083
2013/07/18 13:15:32 [debug] 17641#0: http file cache size: 640074
2013/07/18 13:15:32 [debug] 17641#0: http file cache size: 640050
2013/07/18 13:15:32 [debug] 17641#0: http file cache size: 640042
2013/07/18 13:15:32 [debug] 17641#0: http file cache size: 640026
2013/07/18 13:15:32 [debug] 17641#0: http file cache size: 640011
2013/07/18 13:15:32 [debug] 17641#0: http file cache size: 639997
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640397
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640380
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640368
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640343
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640330
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640306
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640158
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640149
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640139
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640130
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640119
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640110
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640101
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640092
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640072
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640062
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640049
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 640025
2013/07/18 13:15:42 [debug] 17641#0: http file cache size: 639944

Hope it helps...

For the proccesor, the max http file cache size is 640000 (but only for this proxy_cache... i have more!!!)

Thanks.