pylibfdt: Grow the FdtSw buffer geometrically - #189
Merged
Conversation
Every expansion copies the whole tree into a freshly allocated buffer, so growing by a fixed amount makes building a tree cost time quadratic in its size. This is especially painful when assembling larger images with the data inline, such as U-Boot's binman does for FIT images. Grow by at least as much as the tree already holds, which is what variable sized arrays usually do specifically to avoid such excessive copying. With this change, building a Rockchip TF-A+Falcon image whose FIT carries a 31 MiB kernel takes 33.1 s rather than 44.4 s, with binman itself down from 25.3 s to 14.0 s, as 7139 reallocations become 187. The images produced are byte-identical. Signed-off-by: Alexey Charkov <alchark@flipper.net>
Owner
|
I had a momentary misgiving about this: for some very constrained environments where libfdt is used, growing the buffer geometrically might consume too much memory. But.. for those environments would not be where pylibfdt is used. So, merged, thanks. |
This file contains hidden or 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
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
Every expansion copies the whole tree into a freshly allocated buffer, so growing by a fixed amount makes building a tree cost time quadratic in its size. This is especially painful when assembling larger images with the data inline, such as U-Boot's binman does for FIT images.
Grow by at least as much as the tree already holds, which is what variable sized arrays usually do specifically to avoid such excessive copying.
With this change, building a Rockchip TF-A+Falcon image whose FIT carries a 31 MiB kernel takes 33.1 s rather than 44.4 s, with binman itself down from 25.3 s to 14.0 s, as 7139 reallocations become 187. The images produced are byte-identical.