Excessive network traffic - How to reproduce

[Colin D Bennett]

On Thu, 11 Mar 2010 19:49:39 +0100
Joke de Buhr <joke at seiken.de> wrote:

> What exactly is transfered? One revision which causes only a few
> lines to be changed or a set of revisions which?
> 
> A set of revisions might actually result in a quiet large changeset.
> 
> rev: X
>   bzr add file_10MB
>   bzr commit -m "10 MB added"
> rev: X+1
>   bzr rm file_10MB
>   bzr commit -m "file removed"
> rev: X+2
>   bzr commit -m "1 line added (less than 1kb)"
> 
> If the client is add revision X and pulls everything up to revision
> X+2 the 10MB file needs to be transfered but since it's removed the
> within X+1 "visible" change from X to X+1 would only be one line.

True.  But the user is updating only one revision (2250..2251), and it
is a trivial change (no nested merge revision that should cause lots of
traffic, etc.).  According to the GRUB user,

  Response time is faster but the amount of data downloaded is way too
  much for the size of the patch, downloaded 2100 KB for updating from
  rev 2250 to 2251.

In fact, I was able to easily reproduce the problem.  Here's what I did:


SUMMARY OF REPRODUCTION PROCESS

1. Branch the remote GRUB trunk revision 2250 to a local standalone
branch.

2. Pull revision 2251 to the local branch.


DETAILS TO REPRODUCE

/tmp$ bzr branch -r 2250 \
  http://bzr.savannah.gnu.org/r/grub/trunk/grub/grubtest
Branched 2250 revision(s).

/tmp$ bzr -Dbytes -Dfetch pull -r 2251 \
  http://bzr.savannah.gnu.org/r/grub/trunk/grub/ -d grubtest
http://bzr.savannah.gnu.org/r/grub/trunk/grub is permanently
 redirected to http://bzr.savannah.gnu.org/r/grub/trunk/grub/
 M
ChangeLog M  util/i386/pc/grub-setup.c
All changes applied
successfully. Now on revision 2251.
Transferred: 2352KiB (151.7K/s r:2325K w:27K)

Feel free to look at the detailed log of revision 2250..2251 to see
there shouldn't be any hidden huge changes.

Although, just getting the log of these two revisions caused
nearly 3 MB to be transferred and took about one minute on this high
speed office connection.


cdb at svelte:/tmp$ bzr -Dbytes -Dfetch log -r 2250..2251 -n0 -v \
  http://bzr.savannah.gnu.org/r/grub/trunk/grub/
------------------------------------------------------------                   
revno: 2251
author: Matt Kraai <kraai at ftbfs.org>
committer: Colin Watson <cjwatson at ubuntu.com>
branch nick: grub
timestamp: Mon 2010-03-08 22:20:02 +0000
message:
  2010-03-08  Matt Kraai  <kraai at ftbfs.org>
  
  	* util/i386/pc/grub-setup.c (setup): Fix a grammatical error (Debian
  	bug #559005).
modified:
  ChangeLog
  util/i386/pc/grub-setup.c
------------------------------------------------------------
revno: 2250
committer: Vladimir 'phcoder' Serbinenko <phcoder at gmail.com>
branch nick: mainline
timestamp: Sun 2010-03-07 23:02:13 +0100
message:
  2010-03-07  Vladimir Serbinenko  <phcoder at gmail.com>
  
  	* genmoddep.awk: Output all missing symbols and not only first.
modified:
  ChangeLog
  genmoddep.awk
Transferred: 2752KiB (217.3K/s r:2731K w:21K)


Would repacking the repository improve the network access efficiency?

Regards,
Colin
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