Agree with Sam here - we also reduce network calls since we don't need to notify for each failed tryLock, but only for cases when tx will definitely loose.
Thanks! -- Yakov Zhdanov, Director R&D *GridGain Systems* www.gridgain.com 2015-10-16 10:22 GMT+03:00 Semyon Boikov <[email protected]>: > > > > The success ratio with ordered approach is naturally going to be better. > > However, I think the performance will suffer, because queues are > generally > > expensive. Have you tried comparing performance of the queue-based > approach > > vs. the try-lock one? > > > I did not add any new queues and just use existing per-entry list of mvcc > candidates, so ordered approach will definitely perform better than > try-lock. > > On Fri, Oct 16, 2015 at 4:10 AM, Dmitriy Setrakyan <[email protected]> > wrote: > > > On Thu, Oct 15, 2015 at 12:00 AM, Semyon Boikov <[email protected]> > > wrote: > > > > It seems there is better approach to resolve these conflicts to do not > fail > > > all conflicting transactions: > > > - we should order all transactions by some attribute (e.g. all > > transactions > > > already have unique version) > > > - transaction with greater order should always 'win' transaction with > > lower > > > order > > > - per-entry queue with waiting transactions should be sorted by this > > order > > > - when transaction tries to acquire entry lock it is added in waiting > > queue > > > if queue is empty or last waiting transaction have lower order, > otherwise > > > transaction fails > > > > > > With this approach transaction lock assignment is ordered and > > transactions > > > with lower order never wait for transactions with greater order, so > this > > > algorithm should not cause deadlocks. > > > > > > I also created unit test simulating this algorithm and it did not > reveal > > > any issues. Also in this unit tests I measured percent of rollbacks > when > > > concurrent updates have lots of conflicts: with 'try-lock' approach > > percent > > > of rollbacks is ~80%, with new algorithm is ~1% (but of course with > > > real-life test results can be different). > > > > > > > The success ratio with ordered approach is naturally going to be better. > > However, I think the performance will suffer, because queues are > generally > > expensive. Have you tried comparing performance of the queue-based > approach > > vs. the try-lock one? > > >
