Apparent performance regression 8.3@ -> 8.4 at r255966?

[Erik Cederstrand]

Den 07/10/2013 kl. 19.28 skrev David Wolfskill <david at catwhisker.org>:

> In examining the CPU utilization graphs, the CPU generally looks
> about 5% busy for the first 15 minutes; this would be bmake determining
> dependency graphs, I expect.

Is that one process using 100% of one core, or many processes using 5% total?

> Based on earlier work I did, where I was able to do a similar build in a
> native FreeBSD/i386 (no PAE) enviroment on the same hardware (but when
> it still only had 6GB RAM), and I managed to get the build done in 2:47,
> I believe that getting more work done in parallel in this 2:00 period is
> a key to improving performance: the 2:47 result showed that period to be
> a very busy one for the CPU.

You need to know where your bottlenecks are during the build. Since you have lots of RAM, you could try to rule out differences in filesystem access by placing your jail on an mfs and building your software off that. If that improves build times, then you're IO bound at least some of the time. You should be logging disk access along with CPU and memory during the build.

Erik