[distcc] speedup with >2 hosts

[Perochon Sebastien]

If you are using distcc on Cygwin, my experience is that:
- You should use a make software that makes good parallelization like scons.
- If you have 5 hosts (host0 is yours), you should set: host1 host2 host3
host4 in your config line and launch with
"-j=number_of_distant_cpu * number_of_max_jobs_per_client". For you
"-j=4*4=16"

Try with this configuration.
I have done a lot of tests, and it appears to be the best configuration that
I ever have and approach the 45% gain under cygwin !!! 

-----Message d'origine-----
De: SCHMID Stefan [mailto:Stefan.Schmid at cern.ch]
Date: lundi 5 avril 2004 10:00
À: distcc at lists.samba.org
Objet: [distcc] speedup with >2 hosts


hi,

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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