Optimization of the rename case. #666
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
BenBE
reviewed
Apr 9, 2022
geky
added
performance
needs minor version
Rename can be VERY time consuming. One of the reasons is the 4 recursion
level depth of lfs_dir_traverse() seen if a compaction happened during the
rename.
lfs_dir_compact()
size computation
[1] lfs_dir_traverse(cb=lfs_dir_commit_size)
- do 'duplicates and tag update'
[2] lfs_dir_traverse(cb=lfs_dir_traverse_filter, data=tag[1])
- Reaching a LFS_FROM_MOVE tag (here)
[3] lfs_dir_traverse(cb=lfs_dir_traverse_filter, data=tag[1]) <= on 'from' dir
- do 'duplicates and tag update'
[4] lfs_dir_traverse(cb=lfs_dir_traverse_filter, data=tag[3])
followed by the compaction itself:
[1] lfs_dir_traverse(cb=lfs_dir_commit_commit)
- do 'duplicates and tag update'
[2] lfs_dir_traverse(cb=lfs_dir_traverse_filter, data=tag[1])
- Reaching a LFS_FROM_MOVE tag (here)
[3] lfs_dir_traverse(cb=lfs_dir_traverse_filter, data=tag[1]) <= on 'from' dir
- do 'duplicates and tag update'
[4] lfs_dir_traverse(cb=lfs_dir_traverse_filter, data=tag[3])
Yet, analyse shows that levels [3] and [4] don't perform anything
if the callback is lfs_dir_traverse_filter...
A practical example:
- format and mount a 4KB block FS
- create 100 files of 256 Bytes named "/dummy_%d"
- create a 1024 Byte file "/test"
- rename "/test" "/test_rename"
- create a 1024 Byte file "/test"
- rename "/test" "/test_rename"
This triggers a compaction where lfs_dir_traverse was called 148393 times,
generating 25e6+ lfs_bd_read calls (~100 MB+ of data)
With the optimization, lfs_dir_traverse is now called 3248 times
(589e3 lfs_bds_calls (~2.3MB of data)
=> x 43 improvement...
geky
added
v2.5
and removed
needs minor version
|
Thanks again for this! |
Merged
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Rename can be VERY time consuming. One of the reasons is the 4 recursion
level depth of lfs_dir_traverse() seen if a compaction happened during the
rename.
Yet, analyse shows that levels [3] and [4] don't perform anything
if the callback is lfs_dir_traverse_filter...
A practical example:
This triggers a compaction where lfs_dir_traverse was called 148393 times,
generating 25e6+ lfs_bd_read calls (~100 MB+ of data)
With the optimization, lfs_dir_traverse is now called 3248 times
(589e3 lfs_bds_calls (~2.3MB of data)
=> x 43 improvement...