fix: prevents Dragonfly from blocking in epoll during snapshotting #3911
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
The problem - we used file write in non-direct mode when writing snapshots in epoll mode. As a result - lots of data was cached into OS memory. But then during the rename operation, when we rename "xxx.dfs.tmp" into "xxx.dfs", the OS flushes the file caches and the thread is stuck in OS system call rename for a long time. The fix - to use DIRECT mode and to avoid caching the data into OS caches at all. Fixes #3895 Signed-off-by: Roman Gershman <[email protected]>
dranikpg
approved these changes
Oct 12, 2024
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Outdated suggestions cannot be applied.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.
The problem - we used file write in non-direct mode when writing snapshots in epoll mode. As a result - lots of data was cached into OS memory. But then during the rename operation, when we rename "xxx.dfs.tmp" into "xxx.dfs", the OS flushes the file caches and the thread is stuck in OS system call rename for a long time.
The fix - to use DIRECT mode and to avoid caching the data into OS caches at all.
Fixes #3895