~bzr-pqm/bzr/bzr.dev

For a tree holding 2.4.18 (two copies), 2.4.19, 2.4.20

With gzip -9:

mbp@hope% du .bzr

195110  .bzr/text-store

20      .bzr/revision-store

12355   .bzr/inventory-store

216325  .bzr

mbp@hope% du -s .

523128  .

Without gzip:

This is actually a pretty bad example because of deleting and

re-importing 2.4.18, but still not totally unreasonable.

----

linux-2.4.0: 116399 kB

after addding everything: 119505kB

bzr status  2.68s user 0.13s system 84% cpu 3.330 total

bzr commit 'import 2.4.0'  4.41s user 2.15s system 11% cpu 59.490 total

242446  .

122068  .bzr

----

Performance (2005-03-01)

To add all files from linux-2.4.18: about 70s, mostly inventory

serialization/deserialization.

To commit:

- finished, 6.520u/3.870s cpu, 33.940u/10.730s cum

-     134.040 elapsed

Interesting that it spends so long on external processing!  I wonder

if this is for running uuidgen?  Let's try generating things

internally.

Great, this cuts it to 17.15s user 0.61s system 83% cpu 21.365 total

to add, with no external command time.  The commit now seems to spend

most of its time copying to disk.

- finished, 6.550u/3.320s cpu, 35.050u/9.870s cum

-     89.650 elapsed

I wonder where the external time is now?  We were also using uuids()

for revisions.

Let's remove everything and re-add.  Detecting everything was removed

takes 

- finished, 2.460u/0.110s cpu, 0.000u/0.000s cum

-     3.430 elapsed

which may be mostly XML deserialization?

Just getting the previous revision takes about this long:

bzr invoked at Tue 2005-03-01 15:53:05.183741 EST +1100

  by mbp@sourcefrog.net on hope

  arguments: ['/home/mbp/bin/bzr', 'get-revision-inventory', 'mbp@sourcefrog.net-20050301044608-8513202ab179aff4-44e8cd52a41aa705']

  platform: Linux-2.6.10-4-686-i686-with-debian-3.1

- finished, 3.910u/0.390s cpu, 0.000u/0.000s cum

-     6.690 elapsed

Now committing the revision which removes all files should be fast.

- finished, 1.280u/0.030s cpu, 0.000u/0.000s cum

-     1.320 elapsed

Now re-add with new code that doesn't call uuidgen:

- finished, 1.990u/0.030s cpu, 0.000u/0.000s cum

-     2.040 elapsed

16.61s user 0.55s system 74% cpu 22.965 total

Status::

  - finished, 2.500u/0.110s cpu, 0.010u/0.000s cum

  -     3.350 elapsed

And commit::

Now patch up to 2.4.19.  There were some bugs in handling missing

directories, but with that fixed we do much better::

  bzr status  5.86s user 1.06s system 10% cpu 1:05.55 total

This is slow because it's diffing every file; we should use mtimes etc

to make this faster.  The cpu time is reasonable.

I see difflib is pure Python; it might be faster to shell out to GNU

diff when we need it.

Export is very fast::

  - finished, 4.220u/1.480s cpu, 0.010u/0.000s cum

  -     10.810 elapsed

  bzr export 1 ../linux-2.4.18.export1  3.92s user 1.72s system 21% cpu 26.030 total

Now to find and add the new changes::

  - finished, 2.190u/0.030s cpu, 0.000u/0.000s cum

  -     2.300 elapsed

:: 

  bzr commit 'import 2.4.19'  9.36s user 1.91s system 23% cpu 47.127 total

And the result is exactly right.  Try exporting::

  mbp@hope%  bzr export 4 ../linux-2.4.19.export4

  bzr export 4 ../linux-2.4.19.export4  4.21s user 1.70s system 18% cpu 32.304 total

and the export is exactly the same as the tarball.

Now we can optimize the diff a bit more by not comparing files that

have the right SHA-1 from within the commit

For comparison::

  patch -p1 < ../kernel.pkg/patch-2.4.20  1.61s user 1.03s system 13% cpu 19.106 total

Now status after applying the .20 patch.  With full-text verification::

  bzr status  7.07s user 1.32s system 13% cpu 1:04.29 total

with that turned off::

  bzr status  5.86s user 0.56s system 25% cpu 25.577 total

After adding:

  bzr status  6.14s user 0.61s system 25% cpu 26.583 total

Should add some kind of profile counter for quick compares vs slow

compares.

  bzr commit 'import 2.4.20'  7.57s user 1.36s system 20% cpu 43.568

  total

export:  finished, 3.940u/1.820s cpu, 0.000u/0.000s cum,  50.990 elapsed

also exports correctly

now .21

bzr commit 'import 2.4.1'  5.59s user 0.51s system 60% cpu 10.122 total

265520  .

137704  .bzr

import 2.4.2

317758  .

183463  .bzr

with everything through to 2.4.29 imported, the .bzr directory is

1132MB, compared to 185MB for one tree.  The .bzr.log is 100MB!.  So

the storage is 6.1 times larger, although we're holding 30 versions.

It's pretty large but I think not ridiculous.  By contrast the tarball

for 2.4.0 is 104MB, and the tarball plus uncompressed patches are

315MB.

Uncompressed, the text store is 1041MB.  So it is only three times

worse than patches, and could be compressed at presumably roughly

equal efficiency.  It is large, but also a very simple design and

perhaps adequate for the moment.  The text store with each file

individually gziped is 264MB, which is also a very simple format and

makes it less than twice the size of the source tree.

This is actually rather pessimistic because I think there are some

orphaned texts in there.

Measured by du, the compressed full-text store is 363MB; also probably

tolerable.

The real fix is perhaps to use some kind of weave, not so much for

storage efficiency as for fast annotation and therefore possible

annotation-based merge.