Variability in build times.

Uwe Düffert dueffert at uwe-dueffert.de
Mon Oct 18 16:12:50 PDT 2010


On Mon, 18 Oct 2010, Ken Moffat wrote:

> Any thoughts, or alternative suggestions ?
Yes, a few:

Over the past years I took a look at the build times quite often. Never 
systematically, but this is what I experienced: Most of the time I'm 
building a package its because of a new version. I'm using scripts per 
package close to LFS but package version independant and with 
optimization and only run few of them in a row, just as much as I prepared 
packages in advance. As I tend to be impatient, I tail my previous log 
file of the package currently building quite often to see when the package 
building right now is expected to be finished. Most of the time the build 
times are pretty close to the previous attempt, even though I'm building a 
newer version of that package. So in my case a certain package is 
usually built the first time after booting the machine and the build times 
are pretty close even after (minor) version updates.

As others already suspected, I would expect latency (like seek times) of 
the hard drive to have a significant influence on build times and thus 
times might be influenced by caching as well as by significantly changed 
fill level of a partition.

If thats the case then using an SSD should improve the relyability of 
build times. I'll run a series of builds of the same package this night 
(binutils as well for comparison) on a quite fast SSD and report back.

If HD turns out not to be the problem: what about those modern processors 
that overclock some cores automatically? That might easily be influenced 
by running *something* in the background that keeps yet another core 
active and prevents the package building core(s) from overclocking...

Uwe



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