Just a quick test to see how Hexagon performs since there's plenty going on deep within the theme. This was done with Apache Bench comparing Garland with a test sub-theme based on Hexagon (exact copy of the starter theme).
Page caching was disabled since with it enabled, the performance would be pretty much the same. So, no page caching and block caching enabled. The other performance settings have no affect on the relative outcome.
Drupal 6.16 installed with PHP 5.3. I have APC installed so that helps out Hexagon a lot since there are many include calls. This is a known tradeoff. All servers hosting a Drupal install should have some form of PHP caching.
1000 requests, 5 concurrent on the front page listing 10 node teasers. Many modules installed but it should not affect the relative outcome.
ab -n 1000 -c 5 http://localhost/drupal_6/
Garland baseline
Document Length: 26961 bytes
Time taken for tests: 219.349752 seconds
Total transferred: 27424000 bytes
HTML transferred: 26961000 bytes
Requests per second: 4.56 [#/sec] (mean)
Time per request: 1096.749 [ms] (mean)
Time per request: 219.350 [ms] (mean, across all concurrent requests)
Transfer rate: 122.09 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.6 0 12
Processing: 702 1093 160.1 1077 1893
Waiting: 669 1062 160.9 1046 1881
Total: 702 1093 160.1 1077 1893
Percentage of the requests served within a certain time (ms)
50% 1077
66% 1132
75% 1174
80% 1205
90% 1284
95% 1386
98% 1548
99% 1582
100% 1893 (longest request)
Hexagon
Document Length: 27506 bytes
Time taken for tests: 230.595014 seconds
Total transferred: 27969000 bytes
HTML transferred: 27506000 bytes
Requests per second: 4.34 [#/sec] (mean)
Time per request: 1152.975 [ms] (mean)
Time per request: 230.595 [ms] (mean, across all concurrent requests)
Transfer rate: 118.45 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.2 0 3
Processing: 776 1150 131.4 1151 1672
Waiting: 727 1116 131.6 1117 1657
Total: 776 1150 131.4 1151 1672
Percentage of the requests served within a certain time (ms)
50% 1151
66% 1197
75% 1231
80% 1248
90% 1315
95% 1376
98% 1453
99% 1532
100% 1672 (longest request)
There was a slight increase in memory usage. According to Devel, Hexagon uses 4.11 MB vs. 3.96 MB for Garland.
I think this is pretty good considering what Hexagon does. Note that there is a .info setting to turn off theme caching (includes file caching maintained by hexagon & theme registry) for development purposes. Without the caching, the performance is horrible as expected. Make sure it's not disabled when in the wild.