FIO with fsync option issues more DDIR_SYNC commands than expected #1754
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
Issue and root cause: When fsync option is used, the number of flush (or DDIR_SYNC) commands issued is more than the expected number of flush commands. To elaborate: - In the fio config file, consider fsync=1 1. FIO issues 1 write command 2. After write completes, FIO sets last_was_sync variable to false 3. FIO issues 1 flush command 4. FIO keeps issuing flush commands since last_was_sync is still false and this causes more flush commands to be issued than expected 5. last_was_sync is set to true after the flush command completes - The above steps repeats until the workload is completed. Fix: Instead of setting last_was_sync to true after flush command is completed and setting last_was_sync to false after write command is completed, set last_was_sync to true after flush command is issued and set last_was_sync to false after write command is issued. Signed-off-by: Celestine Chen celestinechen@google.com
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Outdated suggestions cannot be applied.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.
FIO with fsync option issues more DDIR_SYNC commands than expected
Issue and root cause
When fsync option is used, the number of flush (or DDIR_SYNC) commands
issued is more than the expected number of flush commands.
To elaborate:
and this causes more flush commands to be issued than expected
Fix
Instead of setting last_was_sync to true after flush command is completed
and setting last_was_sync to false after write command is completed,
set last_was_sync to true after flush command is issued and set
last_was_sync to false after write command is issued.
Signed-off-by: Celestine Chen celestinechen@google.com