Oprofile for Openssl: high variability

[Dario T. <to...@in...>]

Hi Everyone!

I'm recently using oprofile to measure how many CPU instructions are need=
 to encrypt/decrypt a 500MB file using Openssl algorithms. 

Here is a report with the data related to openssl (i.e. licbrypto.so.0.9.=
8) taken every 30s: http://www.ing.unibs.it/~dario.tonesi/grep-dec-aes.tx=
t 

Notice that the number of samples changes a lot every time.

Could anyone explain me why this happens? I thought that if I had used a =
very basic system (with no extra services such as X11 etc.) the data woul=
d have been more stable. 
Is there any solution to make the data more stable?

Thanks a lot
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