Messages in this thread | | | Subject | tcp_recvmesg hang under NET_DMA | From | "Steven J. Magnani" <> | Date | Tue, 09 Mar 2010 14:44:59 -0600 |
| |
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>
| |