SBU calculations

Bruce Dubbs bdubbs at swbell.net
Thu Jun 16 09:21:13 PDT 2005


Matthew Burgess wrote:
> Randy McMurchy wrote:
> 
>> I don't think the last two binutils
>> commands belong in the timing of the SBU, as these two commands
>> aren't involved in the build process of the *binutils* pass1
>> chapter 5 package. These two commands are used as part of the
>> setup for binutils in pass2. To me I see this different than
>> you.
> 
> 
> Well, I'm in violent agreement with you here, Randy.  Like you though,
> I'm not sure it much matters whether the two extra instructions are
> included or not.  I'd prefer they are left out, but I'll defer to
> whatever the lists' consensus is on this one.

Just for reference, this is the script I use for my timing build of
binutils.

Doing some checking, the timing of:

make -C ld clean
make -C ld LIB_PATH=/tools/lib

takes 5.1% of the total build time.  Changing the process to not include
this 5% will increase all the others by this amount.  The largest value,
glibc in Chapter 6, will increase from 12.3 SBU to 12.9 SBU.

The way it is measured will, of course, affect BLFS, but since we have
to rebuild everything and remeasure everything for a released based on a
new LFS anyway, it wouldn't make any difference.

My only concern is telling users how to measure.  I have always thought
of the SBU measurements as the time it takes to accomplish the
procedures in a section of the book, not necessarily the time to build
the 'package'.   If you are not going to measure all the instructions in
Chapter 5's binutils, then this needs to be made very clear in the book.
 For instance, after the make install, add a note like:

"Note: If you are timing your build of binutils to determine a base time
for SBU calculations, do not include the following two instructions in
the timing measurements."

If other sections of the book have instructions that are not included in
the timing, similar notes should be added.  This is cumbersome and IMO
unnecessary.

If I were making the decision, I think I would change the second
paragraph in section 4.5 - About SBU's from the present:

"The SBU measure works as follows. The first package to be compiled from
this book is Binutils in Chapter 5. The time it takes to compile this
package is what will be referred to as the Standard Build Unit or SBU.
All other compile times will be expressed relative to this time."

to:

"The SBU measure works as follows. The first package to be compiled from
this book is Binutils in Chapter 5. The time it takes to execute all the
instructions in that section is what will be referred to as the Standard
Build Unit or SBU. All other compile times will be expressed relative to
this time."

  -- Bruce
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