cluster/afr: Make AFR eager-locking similar to EC Problem: 1) Afr's eager-lock only works for data transactions. 2) When there are conflicting writes, write with conflicting region initiates unlock of eager-lock leading to extra pre-ops and post-ops on the file. When eager-lock goes off, it leads to extra fsyncs for random-write workload in afr. Solution (that is modeled after EC): In EC, when there is a conflicting write, it waits for the current write to complete before it winds the conflicted write. This leads to better utilization of network and disk, because we will not be doing extra xattrops and FSYNCs and inodelk/unlock. I tried to model the solution based on EC's locking, but it is not similar to AFR because we had to keep backward compatibility.
REVIEW: https://review.gluster.org/19503 (cluster/afr: Make AFR eager-locking similar to EC) posted (#8) for review on master by Pranith Kumar Karampuri
REVIEW: https://review.gluster.org/19655 (cluster/afr: Remove compound-fops usage in afr) posted (#1) for review on master by Pranith Kumar Karampuri
REVIEW: https://review.gluster.org/19661 (cluster/afr: Remove unused code paths) posted (#1) for review on master by Pranith Kumar Karampuri
COMMIT: https://review.gluster.org/19661 committed in master by "Ravishankar N" <ravishankar> with a commit message- cluster/afr: Remove unused code paths Removed 1) afr-v1 self-heal locks related code which is not used anymore 2) transaction has some data types that are not needed, so removed them 3) Never used lock tracing available in afr as gluster's network tracing does the job. So removed that as well. 4) Changelog is always enabled and afr is always used with locks, so __changelog_enabled, afr_lock_server_count etc functions can be deleted. 5) transaction.fop/done/resume always call the same functions, so no need to have these variables. BUG: 1549606 Change-Id: I370c146fec2892d40e674d232a5d7256e003c7f1 Signed-off-by: Pranith Kumar K <pkarampu>
COMMIT: https://review.gluster.org/19503 committed in master by "Pranith Kumar Karampuri" <pkarampu> with a commit message- cluster/afr: Make AFR eager-locking similar to EC Problem: 1) Afr's eager-lock only works for data transactions. 2) When there are conflicting writes, write with conflicting region initiates unlock of eager-lock leading to extra pre-ops and post-ops on the file. When eager-lock goes off, it leads to extra fsyncs for random-write workload in afr. Solution (that is modeled after EC): In EC, when there is a conflicting write, it waits for the current write to complete before it winds the conflicted write. This leads to better utilization of network and disk, because we will not be doing extra xattrops and FSYNCs and inodelk/unlock. Moved fd based counters to inode based counters. I tried to model the solution based on EC's locking, but it is not similar to AFR because we had to keep backward compatibility. Lifecycle of lock: ================== First transaction is added to inode->owners list and an inodelk will be sent on the wire. All the next transactions will be put in inode->waiters list until the first transaction completes inodelk and [f]xattrop completely. Once [f]xattrop also completes, all the requests in the inode->waiters list are checked if it conflict with any of the existing locks which are in inode->owners list and if not are added to inode->owners list and resumed with doing transaction. When these transactions complete fop phase they will be moved to inode->post_op list and resume the transactions that were paused because of conflicts. Post-op and unlock will not be issued on the wire until that is the last transaction on that inode. Last transaction when it has to perform post-op can choose to sleep for deyed-post-op-secs value. During that time if any other transaction comes, it will wake up the sleeping transaction and takes over the ownership of the lock and the cycle continues. If the dealyed-post-op-secs expire, then the timer thread will wakeup the sleeping transaction and it will set lock->release to true and starts doing post-op and then unlock. During this time if any other transactions come, they will be put in inode->frozen list. Once the previous unlock comes it will move the frozen list to waiters list and moves the first element from this waiters-list to owners-list and attempts the lock and the cycle continues. This is the general idea. There is logic at the time of dealying and at the time of new transaction or in flush fop to wakeup existing sleeping transactions or choosing whether to delay a transaction etc, which is subjected to change based on future enhancements etc. Fixes: #418 BUG: 1549606 Change-Id: I88b570bbcf332a27c82d2767dfa82472f60055dc Signed-off-by: Pranith Kumar K <pkarampu>
This bug is getting closed because a release has been made available that should address the reported issue. In case the problem is still not fixed with glusterfs-v4.1.0, please open a new bug report. glusterfs-v4.1.0 has been announced on the Gluster mailinglists [1], packages for several distributions should become available in the near future. Keep an eye on the Gluster Users mailinglist [2] and the update infrastructure for your distribution. [1] http://lists.gluster.org/pipermail/announce/2018-June/000102.html [2] https://www.gluster.org/pipermail/gluster-users/