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From: Steven J. Magnani on 9 Mar 2010 15:50
Hi,

I've run into a case where using NET_DMA seems to cause a PUT to a
modified ftpd to hang. AFAICT this is because the NET_DMA design queues
up lots of memcpy operations, but doesn't issue or wait for them (and
thus free the associated skbs) until it is time for tcp_recvmesg() to
return. In a case where userland requests a large read (as is the case
in my modified ftpd), packet transfer can grind to a halt because so
many packets are buffered up and there is no event that causes them to
be freed.

I can submit a patch that would issue pending memcpys and clean up
completed ones around tcp_recvmsg's call to sk_wait_data(), but first I
wanted to understand the design better. Were there specific reasons for
deferring the async operations so long?

Thanks,
------------------------------------------------------------------------
Steven J. Magnani "I claim this network for MARS!
www.digidescorp.com Earthling, return my space modulator!"

#include <standard.disclaimer>


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Prev: ST SPEAr: Added ARM PrimeXsys System Controller SP810 header file
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