]
Andrew Dinn reassigned JBTM-611:
--------------------------------
Assignee: Jonathan Halliday (was: Andrew Dinn)
Performance stilll needs testing.
performance tune transaction reaper
-----------------------------------
Key: JBTM-611
URL:
https://jira.jboss.org/jira/browse/JBTM-611
Project: JBoss Transaction Manager
Issue Type: Task
Security Level: Public(Everyone can see)
Components: Transaction Core
Affects Versions: 4.7.0
Reporter: Jonathan Halliday
Assignee: Jonathan Halliday
Fix For: 4.8.0
In situations where a large number of tx are being created and destroyed concurrently,
the TransactionReaper represents a potential bottleneck due to the necessary
synchronization. For most worklolads this is insignificant as it is dominated by the
objectstore I/O. However, for tx scenarios that don't write the store (1PC, local
resources, etc) it's a potential problem, so it's worth tuning a bit.
There are some things we can do to reduce the workload inside the synchronized scope.
1- ReaperElements are kept in a sorted list, by expiry time. To impose the total ordering
required by SortedSet, items with the same expire time (to the nearest ms) are
distinguished by Uid. This is an expensive comparison. Introduce a sequence number or
other cheap (i.e. int) element to the sort order so as to lessen the comparison (i.e. set
insert/remove) cost.
2 - When a new tx is inserted into the reaper queue, we can avoid waking the reaper and
having it recalculate the sleep interval, provided the new tx is not at the head of the
queue i.e. does not have an expire time earlier than the existing wakeup time.
3 - Some debug logging is performed in synchronized blocks. Whilst this should not be
removed, we can ensure it correctly checks the log threshold configuration, as generating
log output statements unnecessarily is expensive
4 - The transactions and timeouts collections are currently synchronized Collections.
Since almost all access to them is guarded by a lock on the TransactionReaper instance,
they could be replaced by unsynchronized versions with a little work. This may or may not
be helpful.
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