autotuning of send buffer size of a socket

[Shirish Pargaonkar]

Hello,

kernel_sendmsg fails with error EAGAIN, yet I no matter how long I try,
I still get the same error and do not see the send buffer size of a socket
changing (increasing)

The initial buffer sizes are 16384 for send side and 87380 for the receive
side but I see receive side buffer tuning but do not see the same with
send side.

If tcp does not see a need to increase the send buffer size, wonder why I
get EAGAIN error on this non-blocking socket for kernel_sendmsg!

I do subscribe to this mailing list so, please send your responses to this
mail address.

Regards,

Shirish

--------------------------------------------------------------------------------------------------
uname -r
2.6.18-91.el5

 sysctl -a

net.ipv4.tcp_rmem = 4096        87380   4194304
net.ipv4.tcp_wmem = 4096        16384   4194304
net.ipv4.tcp_mem = 98304        131072  196608

net.core.rmem_default = 126976
net.core.wmem_default = 126976
net.core.rmem_max = 131071
net.core.wmem_max = 131071

net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_timestamps = 1
net.ipv4.tcp_moderate_rcvbuf = 1


cat /proc/sys/net/ipv4/tcp_moderate_rcvbuf
1


CIFS VFS: sndbuf 16384 rcvbuf 87380

CIFS VFS: sends on sock 0000000009903100, sendbuf 34776, rcvbuf 190080
stuck for 32 seconds,
error: -11
CIFS VFS: sends on sock 0000000009903a00, sndbuf 34776, rcvbuf 138240
stuck for 32 seconds,
error: -11


CIFS VFS: sends on sock 0000000009903100, sndbuf 34776, rcvbuf 126720
stuck for 64 seconds,
error: -11

CIFS VFS: sends on sock 0000000009903100, sndbuf 34776, rcvbuf 222720
stuck for 256 seconds,
error: -11

I see the socket receive buffer size fluctuating (tcp_moderate_rcvbuf
is 1) but not
the socket send buffer size.
The send buffer size remains fixed, the auto-tuning for send side is
enabled by default,so I do not see it happening here no matter how
long the c ode tries to
kernel_sendmsg after receiving EAGAIN return code.
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