[openib-general] sdp sockets and zcopy?
Roland Dreier
Wed Apr 28 14:09:43 PDT 2004
Abhijit> Hello, when do SDP socket writes translate to Zcopy?
Abhijit> looking at the code (ulp/sdp/*) it seems that write(2) on
Abhijit> (sdp) socket fd's always happen via Bcopy mechanism
Abhijit> unless AIO support is compiled in (and socket aio is used
Abhijit> by the user app). is my understanding correct?
Abhijit> because from the code, write(2) happens via
Abhijit> tsSdpInetSend() which looks to be doing a copy into
Abhijit> kernel space always. (i.e. using Bcopy method).
Hi, Libor (the main author of the SDP code) is out for a few days, so
I will try to answer for him.
You are correct that the current SDP code does zero-copy only for
asynch IO. It should be possible to do blocking reads and writes into
zero-copy, but the current code treats both nonblocking and blocking
IO the same way.
Adding zero-copy for blocking IO has been on our to-do list for a
while but the work has not been done yet. If you're interested in
working on this, you should try and coordinate with Libor when he gets
back next week.
- Roland
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