On 22.11.2014 20:03, Navdeep Parhar wrote:
On Sat, Nov 22, 2014 at 03:09:19PM +0000, Alexander Motin wrote:
Author: mav
Date: Sat Nov 22 15:09:18 2014
New Revision: 274853
URL: https://svnweb.freebsd.org/changeset/base/274853
Log:
For both iSCSI initiator and target increase socket buffer sizes before
establishing connection.
This is a workaround for Chelsio TOE driver, that does not update socket
buffer size in hardware after connection established, and unless that is
done beforehand, kernel code will stuck, attempting to send/receive full
PDU at once.
cxgbe's TOE driver does update the rcv window in the hardware in
response to changes in the socket buffer size (see t4_rcvd in
cxgbe/tom/t4_cpl_io.c).
The bug is that the driver tries to avoid sending too many small updates
to the chip, and instead tries to build up a balance of credits before
an update. This doesn't interact well with some applications that set
the sockbuf size to a high fixed value and then wait for the entire
buffer to fill up before draining it. The driver ends up waiting for
the application to drain the socket's receive buffer so that pru_rcvd
(t4_rcvd) can then send a big batch of credits to the chip, the
application is waiting for the receive to reach its high water mark
before draining the buffer, but the TOE on the chip has shut down the
receive window because it's out of credits. If you see the peer sending
zero window probes and the TOE refusing to budge, then the problem
you've observed is definitely the problem I just described.
Yes, it looks like this. You may find the packet dump with the problem
here: https://people.freebsd.org/~mav/rcvbuf.dump
I'll fix this in the TOE driver. I can send you an early patch in case
you'd like to try out the fix before it gets committed.
Thank you. I'll be happy to try it.
--
Alexander Motin
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