1
For a tree holding 2.4.18 (two copies), 2.4.19, 2.4.20
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12355 .bzr/inventory-store
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This is actually a pretty bad example because of deleting and
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re-importing 2.4.18, but still not totally unreasonable.
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linux-2.4.0: 116399 kB
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after addding everything: 119505kB
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bzr status 2.68s user 0.13s system 84% cpu 3.330 total
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bzr commit 'import 2.4.0' 4.41s user 2.15s system 11% cpu 59.490 total
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Performance (2005-03-01)
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To add all files from linux-2.4.18: about 70s, mostly inventory
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serialization/deserialization.
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- finished, 6.520u/3.870s cpu, 33.940u/10.730s cum
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Interesting that it spends so long on external processing! I wonder
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if this is for running uuidgen? Let's try generating things
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Great, this cuts it to 17.15s user 0.61s system 83% cpu 21.365 total
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to add, with no external command time. The commit now seems to spend
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most of its time copying to disk.
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- finished, 6.550u/3.320s cpu, 35.050u/9.870s cum
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I wonder where the external time is now? We were also using uuids()
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Let's remove everything and re-add. Detecting everything was removed
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- finished, 2.460u/0.110s cpu, 0.000u/0.000s cum
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which may be mostly XML deserialization?
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Just getting the previous revision takes about this long:
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bzr invoked at Tue 2005-03-01 15:53:05.183741 EST +1100
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by mbp@sourcefrog.net on hope
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arguments: ['/home/mbp/bin/bzr', 'get-revision-inventory', 'mbp@sourcefrog.net-20050301044608-8513202ab179aff4-44e8cd52a41aa705']
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platform: Linux-2.6.10-4-686-i686-with-debian-3.1
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- finished, 3.910u/0.390s cpu, 0.000u/0.000s cum
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Now committing the revision which removes all files should be fast.
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- finished, 1.280u/0.030s cpu, 0.000u/0.000s cum
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Now re-add with new code that doesn't call uuidgen:
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- finished, 1.990u/0.030s cpu, 0.000u/0.000s cum
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16.61s user 0.55s system 74% cpu 22.965 total
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- finished, 2.500u/0.110s cpu, 0.010u/0.000s cum
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Now patch up to 2.4.19. There were some bugs in handling missing
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directories, but with that fixed we do much better::
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bzr status 5.86s user 1.06s system 10% cpu 1:05.55 total
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This is slow because it's diffing every file; we should use mtimes etc
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to make this faster. The cpu time is reasonable.
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I see difflib is pure Python; it might be faster to shell out to GNU
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Export is very fast::
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- finished, 4.220u/1.480s cpu, 0.010u/0.000s cum
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bzr export 1 ../linux-2.4.18.export1 3.92s user 1.72s system 21% cpu 26.030 total
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Now to find and add the new changes::
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- finished, 2.190u/0.030s cpu, 0.000u/0.000s cum
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bzr commit 'import 2.4.19' 9.36s user 1.91s system 23% cpu 47.127 total
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And the result is exactly right. Try exporting::
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mbp@hope% bzr export 4 ../linux-2.4.19.export4
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bzr export 4 ../linux-2.4.19.export4 4.21s user 1.70s system 18% cpu 32.304 total
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and the export is exactly the same as the tarball.
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Now we can optimize the diff a bit more by not comparing files that
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have the right SHA-1 from within the commit
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patch -p1 < ../kernel.pkg/patch-2.4.20 1.61s user 1.03s system 13% cpu 19.106 total
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Now status after applying the .20 patch. With full-text verification::
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bzr status 7.07s user 1.32s system 13% cpu 1:04.29 total
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with that turned off::
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bzr status 5.86s user 0.56s system 25% cpu 25.577 total
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bzr status 6.14s user 0.61s system 25% cpu 26.583 total
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Should add some kind of profile counter for quick compares vs slow
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bzr commit 'import 2.4.20' 7.57s user 1.36s system 20% cpu 43.568
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export: finished, 3.940u/1.820s cpu, 0.000u/0.000s cum, 50.990 elapsed
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also exports correctly
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bzr commit 'import 2.4.1' 5.59s user 0.51s system 60% cpu 10.122 total
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with everything through to 2.4.29 imported, the .bzr directory is
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1132MB, compared to 185MB for one tree. The .bzr.log is 100MB!. So
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the storage is 6.1 times larger, although we're holding 30 versions.
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It's pretty large but I think not ridiculous. By contrast the tarball
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for 2.4.0 is 104MB, and the tarball plus uncompressed patches are
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Uncompressed, the text store is 1041MB. So it is only three times
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worse than patches, and could be compressed at presumably roughly
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equal efficiency. It is large, but also a very simple design and
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perhaps adequate for the moment. The text store with each file
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individually gziped is 264MB, which is also a very simple format and
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makes it less than twice the size of the source tree.
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This is actually rather pessimistic because I think there are some
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orphaned texts in there.
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Measured by du, the compressed full-text store is 363MB; also probably
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The real fix is perhaps to use some kind of weave, not so much for
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storage efficiency as for fast annotation and therefore possible
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annotation-based merge.
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Now we have recursive add, add is much faster. Adding all of the
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linux 2.4.19 kernel tree takes only
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finished, 5.460u/0.610s cpu, 0.010u/0.000s cum, 6.710 elapsed
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However, the store code currently flushes to disk after every write,
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which is probably excessive. So a commit takes
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finished, 8.740u/3.950s cpu, 0.010u/0.000s cum, 156.420 elapsed
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Status is now also quite fast, depsite that it still has to read all
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mbp@hope% bzr status ~/work/linux-2.4.19
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bzr status 5.51s user 0.79s system 99% cpu 6.337 total
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strace shows much of this is in write(2), probably because of
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logging. With more buffering on that file, removing all the explicit
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flushes, that is reduced to
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mbp@hope% time bzr status
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bzr status 5.23s user 0.42s system 97% cpu 5.780 total
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which is mostly opening, stating and reading files, as it should be.
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Still a few too many stat calls.
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Now fixed up handling of root directory.
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Without flushing everything to disk as it goes into the store:
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mbp@hope% bzr commit -m 'import linux 2.4.19'
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bzr commit -m 'import linux 2.4.19' 8.15s user 2.09s system 53% cpu 19.295 total
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mbp@hope% time bzr diff
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bzr diff 5.80s user 0.52s system 69% cpu 9.128 total
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mbp@hope% time bzr status
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bzr status 5.64s user 0.43s system 68% cpu 8.848 total
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patch -p1 < ../linux.pkg/patch-2.4.20 1.67s user 0.96s system 90% cpu 2.905 total
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The diff changes 3462 files according to diffstat.
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branch format: Bazaar-NG branch, format 0.0.4
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614 versioned subdirectories
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That is, 3510 entries have changed, but there are 48 changed
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directories so the count is exactly right!
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bzr commit -v -m 'import 2.4.20' 8.23s user 1.09s system 48% cpu 19.411 total
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Kind of strange that this takes as much time as committing the whole
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thing; I suppose it has to read every file.
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This shows many files as being renamed; I don't know why that would
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2969 files changed, 366643 insertions(+), 147759 deletions(-)
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2969 files changed, 372168 insertions(+), 153284 deletions(-)
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I wonder why it is not exactly the same? Maybe because the python
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diff algorithm is a bit differnt to GNU diff.
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full check, retrieving all file texts once for the 2.4 kernel branch
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takes 10m elapsed, 1m cpu time. lots of random IO and seeking.
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mbp@hope% time python =bzr deleted --show-ids
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README README-fa1d8447b4fd0140-adbf4342752f0fc3
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python =bzr deleted --show-ids 1.55s user 0.09s system 96% cpu 1.701 total
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mbp@hope% time python -O =bzr deleted --show-ids
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README README-fa1d8447b4fd0140-adbf4342752f0fc3
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python -O =bzr deleted --show-ids 1.47s user 0.10s system 101% cpu 1.547 total
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mbp@hope% time python -O =bzr deleted --show-ids
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README README-fa1d8447b4fd0140-adbf4342752f0fc3
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python -O =bzr deleted --show-ids 1.49s user 0.07s system 99% cpu 1.565 total
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mbp@hope% time python =bzr deleted --show-ids
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README README-fa1d8447b4fd0140-adbf4342752f0fc3
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python =bzr deleted --show-ids 1.55s user 0.08s system 99% cpu 1.637 total
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small but significant improvement from Python -O
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Loading a large inventory through cElementTree is pretty quick; only
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about 0.117s. By contrast reading the inventory into our data
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structure takes about 0.7s.
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So I think the problem must be in converting everything to
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InventoryEntries and back again every time.
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Thought about that way it seems pretty inefficient: why create all
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those objects when most of them aren't called on most invocations?
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Instead perhaps the Inventory object should hold the ElementTree and
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pull things out of it only as necessary? We can even have an index
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pointing into the ElementTree by id, path, etc.
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bzr deleted 1.46s user 0.08s system 98% cpu 1.561 total
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Alternatively maybe keep an id2path and path2id cache? Keeping it
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coherent may be hard...
added
removed
notes/performance.txt
