On Fri, 5 Jan 2007, Darren Reed wrote:
If one were to use the socket option SO_RCVBUF, there is an
expectation that the system will at some point fill that buffer if
there is enough data written before I do a read.
Assuming that the receive-buffer can be fully filled with user-data is
wrong. ;) Just cause there's only a few bytes in the receive buffer does
/not/ mean the receive buffer has space left. :)
This application, presuming it can also run over non-TCP-fusion, also is
assuming:
- how the system accounts non-data bytes to the receive buffer
- deeply implementation specific and un-application-relevant
- in how many packets the data is transferred possibly (not
deterministic, even if the app /does/ know exactly how the system
buffers)
Even if this application is only ever meant to run on Solaris and TCP
loopback, there's no guarantee that:
- the application actually will get tcp fusion (various administrative
actions can cause fusion to be disabled, e.g. do_tcp_fusion), if it
gets TCP the buffering behaviour will be completely different again.
- that the admin won't have tweaked tcp_fusion_burst_min
We document the above in Bigadmin. ;)
Or have I got the wrong end of the stick?
regards,
--
Paul Jakma,
Network Approachability, KISS. Sun Microsystems, Dublin, Ireland.
http://opensolaris.org/os/project/quagga tel: EMEA x19190 / +353 1 819 9190
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