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Message-Id: <20100318.203644.102533317.davem@davemloft.net> Date: Thu, 18 Mar 2010 20:36:44 -0700 (PDT) From: David Miller <davem@...emloft.net> To: steve@...idescorp.com Cc: netdev@...r.kernel.org, kuznet@....inr.ac.ru, pekkas@...core.fi, jmorris@...ei.org, yoshfuji@...ux-ipv6.org, kaber@...sh.net, linux-kernel@...r.kernel.org Subject: Re: [PATCH] NET_DMA: free skbs periodically From: "Steven J. Magnani" <steve@...idescorp.com> Date: Tue, 16 Mar 2010 10:22:44 -0500 > Under NET_DMA, data transfer can grind to a halt when userland issues a > large read on a socket with a high RCVLOWAT (i.e., 512 KB for both). > This appears to be 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. > The socket hangs when its TCP window goes to zero before enough data is > available to satisfy the read. > > Periodically issue asynchronous memcpy operations, and free skbs for ones > that have completed, to prevent sockets from going into zero-window mode. > > Signed-off-by: Steven J. Magnani <steve@...idescorp.com> Can one of the NET DMA folks review this. It's a pretty fundamental problem with how this stuff works it seems. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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