Ceph » RADOS

Running RBD small IO performance tests against a mostly sparse image shows that the Objecter is throwing/catching a buffer decode error. The object doesn't exist so the op failed with -ENOENT, but the sparse_read finisher is still run and attempts to decode an empty bufferlist. This results in a non-negligible amount of CPU being wasted on throwing and immediately catching an exception when instead the decode should never have been attempted since the object didn't exist.

                  - 14.21% Objecter::handle_osd_op_reply                                                                                                                                
                     - 7.64% Context::complete                                                                                                                                          
                        - 6.83% ObjectOperation::C_ObjectOperation_sparse_read::finish                                                                                                  
                           - 6.15% ceph::buffer::list::iterator_impl<false>::copy                                                                                                       
                              - 5.94% __cxa_throw                                                                                                                                       
                                 - 5.75% _Unwind_RaiseException