[blfs-dev] SBUs - was Re: #3982: Firefox-23.0.1/Xulrunner-23.0.1

Ken Moffat zarniwhoop at ntlworld.com
Thu Aug 22 07:29:56 PDT 2013

On Thu, Aug 22, 2013 at 09:45:03AM -0300, Fernando de Oliveira wrote:
> Em 21-08-2013 19:48, Ken Moffat escreveu:
> I will write down things that I think. I may be wrong, so, please tell
> me, if I am.
> SBU is good, necessary. SBU can never be trusted completely. Can never
> be accurate. This host has SBU=133s (about measurement method, see
> below), but 7.4-rc1, in a VM, in this same host, reported SBU=120s,
> yesterday, so one must be wrong, or, inaccurate.

 Or something else was using the processor when you first measured,
or conceivably something in the kernel or VM improved.  Perhaps you
gave it more memory.
> I have a script to generate the SBUs. However, each time it is executed
> in the same machine, the value is different, most of times by small
> amounts, but eventually, by large amounts (cannot remember if it could
> be double the value or such). Perhaps the machines have their own
> "temper" :-), they sometimes get slowing down, tired, have to leave X,
> clean swap, restart video card module, restart VM services,logout, get
> back... But, SBU is necessary, is a very good invention, cannot see how
> it could be done differently, and gives an order of magnitude for the build.

 It will always differ, but hopefully not by more than a few
seconds.  OTOH if you only had one CPU then any other tasks running
will make a noticeable difference.
> About the method, I do aa thing similar to you, but run the script as
> normal user and install using DESTDIR. I believe this should not differ
> much from executing as root,  in an empty tools, but if it is really
> very different, please, tell me.

 Sorry - yes, I do this too when measuring for the book.  By that
time I've already installed the package and (hopefully) noticed if
it works ok  If you ever look at the wiki you might come across a
few packages where I've noted variations of DESTDIR (typically
> About the SBUs for mozilla's. I recall one day, VM with, perhaps, 512MB
> of RAM, it was taking much much longer than previous versions. So
> started watching libxul linking (did not understand it was linking, at
> that time). It was taking what I recall much more than double the time
> as previous ones (probably wrong memory is). Said in earlier post it had
> 1GB, but seems I started using them with 512MB. Point is, any changes,
> SBU different.

 Yes, agreed.

das eine Mal als Tragödie, dieses Mal als Farce

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