On Tue, Dec 2, 2014 at 10:17 AM, Andreas Bluemle <[email protected]> wrote: > Hi, > > during code profiling using LTTng, I encounter that during > processing of write requests to the cluster, the ceph-osd > spends a lot of time in the ReplicatedPG::log_operation > before the the actual writes to journal and object > in the FileStore are triggered. > > This happens in ReplicatedBackend::submit_transaction. > > What I wonder is > - what is the purpose of the log_operation? > If I am not mistaken, then it is neither the write-to-journal > nor the write-to-object; both of these are triggered from > the queue_operation following that log_operation.
This is setting up the changes to the pg log, and encoding them into the transaction. > - can the sequence between the log_operation and > the actual queue_operation be reversed in > ReplicatedBackend::submit_transaction? Nope, it needs to go into the transaction and get journaled. I'm kind of surprised this is a big time sink, but there is a lot of encoding so if you're running against a fast system I suppose it could be relatively large. -Greg -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
