On 10/15/2013 10:04 PM, Florian Weimer wrote:
On 10/15/2013 09:10 PM, Chris Adams wrote:
Once upon a time, Jan Kratochvil <jan.kratochvil@xxxxxxxxxx> said:
It depends, for example in this case prelink saves 33% of time (and
battery):
i=0;time while [ $i -lt 1000 ];do /usr/bin/gnome-open --help
&>/dev/null;i=$[$i+1];done
Do you really run "gnome-open --help" 1000 times per reasonable unit of
time (or ever)? Please stop using bogus comparisons and highly
contrived tests. They do nothing to help your argument.
This isn't totally invalid. I assume that some shell scripts with tight
loops are the only thing that actually benefits from prelinking today.
People write those, unfortunately.
I'm attaching a deliberately badly written script which should be fairly
representative, alas. I can' benchmark it right now because the system
isn't idle, but if someone else wants to have a go at it, be my guest.
I've no run this script (on Fedora 19 x86_64) with an input file
calibrated to run in roughly ten seconds (with prelink), both with and
without prelink, each 30 times. R reports this for the wall-clock time:
t.test(prelink1noff$V1, noprelink1noff$V1)
Welch Two Sample t-test
data: prelink1noff$V1 and noprelink1noff$V1
t = -50.8453, df = 57.923, p-value < 2.2e-16
alternative hypothesis: true difference in means is not equal to 0
95 percent confidence interval:
-0.9337006 -0.8629660
sample estimates:
mean of x mean of y
10.05300 10.95133
This suggests that there is a statistically significant difference in
favor of prelinking, of about 0.9 seconds for a 10 second run.
So even in that totally artificial case, we gain very little,
considering the trouble that prelink is.
--
Florian Weimer / Red Hat Product Security Team
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