diff options
| author | William Manley <will@williammanley.net> | 2018-06-22 15:28:49 +0100 |
|---|---|---|
| committer | Atomic Bot <atomic-devel@projectatomic.io> | 2018-07-09 13:10:51 +0000 |
| commit | c7b12a8730260c66bc96363a3a3c5805b325bac8 (patch) | |
| tree | ec4a54c682086e324442e34aad2979ce365486c2 /apidoc | |
| parent | 11eb0bd227ffa1a3300e4dbde3da288a7d9d41ae (diff) | |
| download | ostree-c7b12a8730260c66bc96363a3a3c5805b325bac8.tar.gz | |
ostree repo commit: Speed up composing trees with `--tree=ref`
Running `ostree commit --tree=ref=a --tree=dir=b` involves reading the
whole of a into an `OstreeMutableTree` before composing `b` on top. This
is inefficient if a is a complete rootfs and b is just touching one file.
We process O(size of a + size of b) directories rather than
O(number of touched dirs).
This commit makes `ostree commit` more efficient at composing multiple
directories together. With `ostree_mutable_tree_fill_empty_from_dirtree`
we create a lazy `OstreeMutableTree` which only reads the underlying
information from disk when needed. We don't need to read all the
subdirectories just to get the checksum of a tree already checked into the
repo.
This provides great speedups when composing a rootfs out of multiple other
rootfs as we do in our build system. We compose multiple containers
together with:
ostree commit --tree=ref=base-rootfs --tree=ref=container1 --tree=ref=container2
and it is much faster now.
As a test I ran
time ostree --repo=... commit --orphan --tree=ref=big-rootfs --tree=dir=modified_etc
Where modified_etc contained a modified sudoers file under /etc. I used
`strace` to count syscalls and I seperatly took timing measurements. To
test with a cold cache I ran
sync && echo 3 | sudo tee /proc/sys/vm/drop_caches
Results:
| | Before | After |
| -------------------- | ------ | ----- |
| Time (cold cache) | 8.1s | 0.12s |
| Time (warm cache) | 3.7s | 0.08s |
| `openat` calls | 53589 | 246 |
| `fgetxattr` calls | 78916 | 0 |
I'm not sure if this will have some negative interaction with the
`_ostree_repo_commit_modifier_apply` which is short-circuited here. I
think it was disabled for `--tree=ref=` anyway, but I'm not certain. All
the tests pass anyway.
I originally implemented this in terms of the `OstreeRepoFile` APIs, but
it was *way* less efficient, opening and reading many files unnecessarily.
Closes: #1643
Approved by: cgwalters
Diffstat (limited to 'apidoc')
| -rw-r--r-- | apidoc/ostree-sections.txt | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/apidoc/ostree-sections.txt b/apidoc/ostree-sections.txt index 74c1fba0..2e174244 100644 --- a/apidoc/ostree-sections.txt +++ b/apidoc/ostree-sections.txt @@ -250,6 +250,8 @@ OstreeLzmaDecompressorClass <FILE>ostree-mutable-tree</FILE> OstreeMutableTree ostree_mutable_tree_new +ostree_mutable_tree_new_from_checksum +ostree_mutable_tree_check_error ostree_mutable_tree_set_metadata_checksum ostree_mutable_tree_get_metadata_checksum ostree_mutable_tree_set_contents_checksum @@ -261,6 +263,7 @@ ostree_mutable_tree_ensure_parent_dirs ostree_mutable_tree_walk ostree_mutable_tree_get_subdirs ostree_mutable_tree_get_files +ostree_mutable_tree_fill_empty_from_dirtree <SUBSECTION Standard> OSTREE_MUTABLE_TREE OSTREE_IS_MUTABLE_TREE |