i'm using a system of five dual-CPU distcc-hosts for distributed compilation. with all my projects, one additional host is very useful but the third to fifth hardly contribute anything at all. moreover, there is quite some variation in the execution time although all hosts do nothing else besides compilation (maybe because of the sleeping times when hosts are locked?). it is therefore also hard to tell which -j-option is the best for a given number of hosts...
all in all, with 5 hosts (10 cpu's) i hardly get any speedups greater than 2 (compared to one host, i.e. 2 cpu's). do you have an idea where i do something wrong?
my test results (secs for execution) for two projects (see http://pool.cern.ch/ and http://cobra.web.cern.ch/cobra/) :
(rows: local gcc, distcc 1 host, distcc 2 hosts, ..., distcc 5 hosts)
POOL_1_5_0 -j1 524.109 403.182 423.12 423.022 423.161 432.99
POOL_1_5_0 -j2 245.48 238.306 224.87 225.753 223.703 227.354
POOL_1_5_0 -j3 207.163 214.53 184.347 170.019 170.547 165.265
POOL_1_5_0 -j4 198.435 204.426 160.376 158.509 145.761 141.132
POOL_1_5_0 -j5 192.305 199.78 151.336 138.679 136.743 129.47
POOL_1_5_0 -j6 190.449 194.69 148.778 121.158 119.138 121.851
POOL_1_5_0 -j7 189.591 188.442 132.294 120.255 114.332 118.116
POOL_1_5_0 -j8 184.573 186.787 139.937 125.054 115.501 107.754
POOL_1_5_0 -j9 183.21 186.79 131.781 114.878 116.696 119.562
POOL_1_5_0 -j10 184.492 184.814 119.932 110.929 124.242 105.603
POOL_1_5_0 -j20 184.693 184.689 119.269 107.858 112.403 98.068
POOL_1_5_0 -j30 187.706 187.804 121.199 105.368 101.697 111.87
POOL_1_5_0 -j40 184.883 185.327 120.914 113.608 107.051 104.128
COBRA_7_6_2 -j1 2008.935 2001.957 2043.355 2019.084 1981.221 1857.332
COBRA_7_6_2 -j2 1146.983 1147.815 1155.362 1103.564 1115.603 1039.243
COBRA_7_6_2 -j3 1003.312 1021.819 896.704 885.989 891.698 763.843
COBRA_7_6_2 -j4 938.189 955.181 745.606 743.038 748.7 696.498
COBRA_7_6_2 -j5 906.81 920.835 723.033 722.671 720.449 609.371
COBRA_7_6_2 -j6 890.789 894.505 653.573 641.013 654.377 549.385
COBRA_7_6_2 -j7 888.649 884.612 640.566 648.136 639.796 539.807
COBRA_7_6_2 -j8 919.197 916.565 603.441 615.01 593.078 514.258
COBRA_7_6_2 -j9 933.188 878.929 623.407 618.13 601.532 494.551
COBRA_7_6_2 -j10 876.65 872.363 595.856 592.644 554.659 505.846
COBRA_7_6_2 -j20 869.178 920.754 589.309 591.447 555.204 462.276
COBRA_7_6_2 -j30 879.127 943.271 572.677 570.154 515.484 460.046
COBRA_7_6_2 j40 860.174 878.043 580.813 583.662 524.954 455.205
cheers, stefan
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