Jon Paul Maloy 365ad353c2 tipc: reduce risk of user starvation during link congestion ... The socket code currently handles link congestion by either blocking and trying to send again when the congestion has abated, or just returning to the user with -EAGAIN and let him re-try later. This mechanism is prone to starvation, because the wakeup algorithm is non-atomic. During the time the link issues a wakeup signal, until the socket wakes up and re-attempts sending, other senders may have come in between and occupied the free buffer space in the link. This in turn may lead to a socket having to make many send attempts before it is successful. In extremely loaded systems we have observed latency times of several seconds before a low-priority socket is able to send out a message. In this commit, we simplify this mechanism and reduce the risk of the described scenario happening. When a message is attempted sent via a congested link, we now let it be added to the link's backlog queue anyway, thus permitting an oversubscription of one message per source socket. We still create a wakeup item and return an error code, hence instructing the sender to block or stop sending. Only when enough space has been freed up in the link's backlog queue do we issue a wakeup event that allows the sender to continue with the next message, if any. The fact that a socket now can consider a message sent even when the link returns a congestion code means that the sending socket code can be simplified. Also, since this is a good opportunity to get rid of the obsolete 'mtu change' condition in the three socket send functions, we now choose to refactor those functions completely. Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com> Acked-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net>		2017-01-03 11:13:05 -05:00
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addr.c
addr.h
bcast.c	tipc: reduce risk of user starvation during link congestion	2017-01-03 11:13:05 -05:00
bcast.h	tipc: fix broadcast link synchronization problem	2016-10-29 17:21:09 -04:00
bearer.c	tipc: check minimum bearer MTU	2016-12-02 14:03:20 -05:00
bearer.h	tipc: check minimum bearer MTU	2016-12-02 14:03:20 -05:00
core.c	netns: make struct pernet_operations::id unsigned int	2016-11-18 10:59:15 -05:00
core.h	netns: make struct pernet_operations::id unsigned int	2016-11-18 10:59:15 -05:00
discover.c
discover.h
eth_media.c
ib_media.c
Kconfig
link.c	tipc: reduce risk of user starvation during link congestion	2017-01-03 11:13:05 -05:00
link.h
Makefile
monitor.c	tipc: improve sanity check for received domain records	2016-11-25 20:06:18 -05:00
monitor.h
msg.c	[iov_iter] new primitives - copy_from_iter_full() and friends	2016-12-05 14:33:36 -05:00
msg.h	tipc: reduce risk of user starvation during link congestion	2017-01-03 11:13:05 -05:00
name_distr.c	tipc: fix broadcast link synchronization problem	2016-10-29 17:21:09 -04:00
name_distr.h
name_table.c	tipc: modify struct tipc_plist to be more versatile	2017-01-03 11:13:05 -05:00
name_table.h	tipc: modify struct tipc_plist to be more versatile	2017-01-03 11:13:05 -05:00
net.c
net.h
netlink_compat.c	genetlink: mark families as __ro_after_init	2016-10-27 16:16:09 -04:00
netlink.c	genetlink: mark families as __ro_after_init	2016-10-27 16:16:09 -04:00
netlink.h
node.c	tipc: reduce risk of user starvation during link congestion	2017-01-03 11:13:05 -05:00
node.h
server.c
server.h
socket.c	tipc: reduce risk of user starvation during link congestion	2017-01-03 11:13:05 -05:00
socket.h
subscr.c
subscr.h
sysctl.c
udp_media.c	tipc: check minimum bearer MTU	2016-12-02 14:03:20 -05:00
udp_media.h