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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 |
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.gitignore | ||
Makefile.am | ||
ostree-docs.xml | ||
ostree-experimental-sections.txt | ||
ostree-sections.txt |