例：运行 ./http_load -rate 5 -seconds 10 url.txt 结果： 44 fetches, 6 max parallel, 2.43038e+06 bytes, in 10 seconds 55236 mean bytes/connection 4.4 fetches/sec, 243038 bytes/sec msecs/connect: 37.7194 mean, 84.635 max, 26.76 min msecs/first-response: 37.9979 mean, 50.72 max, 28.228 min HTTP response codes: code 200 -- 44
