Lockhammer clh spinlocks from Arm #43
Merged
Conversation
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
Integration with minor bug fixes and new colon delimiter for -o option
Sync with upstream before checking in new workloads
CLH is a starvation-free queue spinlock which has FCFS (first come, first served) order like MCS spinlock. CLH spinlock is simpler than MCS spinlock, and each thread is spinning on its previous node's wait flag. Our CLH spinlock has an optional parameter to disable SEVL and WFE.
Contributor
|
Can one of the admins verify this patch? |
added 5 commits
August 8, 2018 12:01
clh_unlock() now returns node->prev directly. Also disable wfe() for all non-aarch64 systems by default.
Now sweep mode has 5 tests: -c 0ns -p 0ns (heavy load) -c 200ns -p 0ns (baseline) -c 1000ns -p 0ns (baseline) -c 200ns -p 1000ns (median load) -c 1000ns -p 5000ns (light load)
Because each thread may finish and join randomly, some thread may reference other thread's __thread (thread local storage) even if that thread has been joined (removed). This will cause segmentation fault. Another issue is DDEBUG mode printf may cause clh_spinlock live lock if thread number is too high.
This may reflect the real unlock state
Need to save node->prev to a temporary variable, because once clh_unlock() has been called, the current clh_node may be used by another thread for many times and node->prev value might be changed. Therefore two thread may end up using the same clh_node next time and cause circular linked list problem (live-lock on the same clh_node)
Contributor
Author
|
Verified and Tested on both dual-socket Arm and x86 system, all sweep test passed, performance similar to MCS spinlock. |
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.
Initial patch for CLH queue spinlock, which is simpler than MCS but has similar performance.