id,summary,reporter,owner,description,type,status,priority,milestone,component,version,severity,resolution,keywords,cc
147,Slow method invocations with reference arguments,Bernhard Haumacher (haui at haumacher dot de),,"Passing a ""new"" remote reference in a remote method invocation is slow. A new remote reference is one that was just created (by passing an old one in a remote method invocation). While passing an old reference costs time(ping(ref)) - time(ping()) = 238.974 - 93.008 = 145.966 us, the cost of passing the new reference in the pingPong() method costs time(pingPong(ref)) - time(pingPong()) - time(passing-old-ref) = 1049.859 - 264.632 - 145.966 = 639.261 us.


{{{
# JP/KaRMI/RemoteResident/DistributedThreads/ParaStation/Myrinet
void ping()                   :    93.008us
void pingPong()               :   264.632us
void ping(ref)                :   238.974us
void pingPong(ref)            :  1049.859us
void ping2(ref)               :  1020.029us
synchronized(r)               :   168.109us
}}}
The reason for that is the hierarchical garbage collector. It uses so called bridge objects for locally (per remote reference) counting the number of references passed to other VMs. But a bridge object can also serve as a communication proxy. Such bridge object requires more initialization that can be done lazily. When initializing bridge objects lazily, the reference passing overhead can be greatly reduced:


{{{
# JP/KaRMI/RemoteResident/DistributedThreads/ParaStation/Myrinet
void ping()                   :    93.441 us +-  1.101us
void pingPong()               :   260.262 us +-  4.386us
void ping(ref)                :   237.287 us +- 20.265us
ref ping(ref)                 :   358.264 us +- 55.810us
void pingPong(ref)            :   536.787 us +- 36.892us
void ping2(ref)               :   565.000 us +- 50.006us
synchronized(r)               :   172.106 us +-  0.168us
}}}

{{{
# JP/KaRMI/RemoteResident/DistributedThreads/TCP/Ethernet100
void ping()                   :   200.295us +-  1.855us
void pingPong()               :   416.443us +-  4.801us
void ping(ref)                :   328.531us +- 24.257us
ref ping(ref)                 :   538.933us +-111.142us
void pingPong(ref)            :   709.770us +- 69.030us
void ping2(ref)               :   730.650us +- 79.527us
synchronized(r)               :   359.134us +-  0.326us
}}}
For comparison here is the corresponding section form the RMI benchmark:


{{{
# JP/RMI/RemoteResident/TCP/Ethernet100
void ping()                   :   295.238us +-  1.102us
void pingPong()               :   628.288us +- 11.353us
void ping(ref)                :  1090.861us +-138.926us
ref ping(ref)                 :  2255.411us +-135.265us
void pingPong(ref)            :  2224.026us +- 58.650us
void ping2(ref)               :  2232.143us +- 61.107us
synchronized(r)               :   586.212us +-  0.719us
}}}


'''fixed''' since 1.07a.
",defect,closed,normal,1.07a,uka.karmi,,normal,fixed,,