[ Upstream commit b49960a05e32121d29316cfdf653894b88ac9190 ] tcp_adv_win_scale default value is 2, meaning we expect a good citizen skb to have skb->len / skb->truesize ratio of 75% (3/4) In 2.6 kernels we (mis)accounted for typical MSS=1460 frame : 1536 + 64 + 256 = 1856 'estimated truesize', and 1856 * 3/4 = 1392. So these skbs were considered as not bloated. With recent truesize fixes, a typical MSS=1460 frame truesize is now the more precise : 2048 + 256 = 2304. But 2304 * 3/4 = 1728. So these skb are not good citizen anymore, because 1460 < 1728 (GRO can escape this problem because it build skbs with a too low truesize.) This also means tcp advertises a too optimistic window for a given allocated rcvspace : When receiving frames, sk_rmem_alloc can hit sk_rcvbuf limit and we call tcp_prune_queue()/tcp_collapse() too often, especially when application is slow to drain its receive queue or in case of losses (netperf is fast, scp is slow). This is a major latency source. We should adjust the len/truesize ratio to 50% instead of 75% This patch : 1) changes tcp_adv_win_scale default to 1 instead of 2 2) increase tcp_rmem[2] limit from 4MB to 6MB to take into account better truesize tracking and to allow autotuning tcp receive window to reach same value than before. Note that same amount of kernel memory is consumed compared to 2.6 kernels. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Neal Cardwell <ncardwell@google.com> Cc: Tom Herbert <therbert@google.com> Cc: Yuchung Cheng <ycheng@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
v2, based on Jay's review. I kept the 'link must be up' part, because this is enforced in the code. Signed-off-by: Nicolas de Pesloüan <nicolas.2p.debian@free.fr> Signed-off-by: Jay Vosburgh <fubar@us.ibm.com> cc: Andy Gospodarek <andy@greyhouse.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Just fixed typo of sample code in packet_mmap.txt Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn> Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Fix some trivial typos. Signed-off-by: Shan Wei <shanwei88@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Since commit c5ed63d66f24(tcp: fix three tcp sysctls tuning), sysctl_max_syn_backlog is determined by tcp_hashinfo->ehash_mask, and the minimal value is 128, and it will increase in proportion to the memory of machine. The original description for tcp_max_syn_backlog and sysctl_max_syn_backlog are out of date. Changelog: V2: update description for sysctl_max_syn_backlog Signed-off-by: Weiping Pan <panweiping3@gmail.com> Reviewed-by: Shan Wei <shanwei88@gmail.com> Acked-by: Neil Horman <nhorman@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Open vSwitch is a multilayer Ethernet switch targeted at virtualized environments. In addition to supporting a variety of features expected in a traditional hardware switch, it enables fine-grained programmatic extension and flow-based control of the network. This control is useful in a wide variety of applications but is particularly important in multi-server virtualization deployments, which are often characterized by highly dynamic endpoints and the need to maintain logical abstractions for multiple tenants. The Open vSwitch datapath provides an in-kernel fast path for packet forwarding. It is complemented by a userspace daemon, ovs-vswitchd, which is able to accept configuration from a variety of sources and translate it into packet processing rules. See http://openvswitch.org for more information and userspace utilities. Signed-off-by: Jesse Gross <jesse@nicira.com>
Rick Jones reported that TCP_CONGESTION sockopt performed on a listener was ignored for its children sockets : right after accept() the congestion control for new socket is the system default one. This seems an oversight of the initial design (quoted from Stephen) Based on prior investigation and patch from Rick. Reported-by: Rick Jones <rick.jones2@hp.com> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> CC: Stephen Hemminger <shemminger@vyatta.com> CC: Yuchung Cheng <ycheng@google.com> Tested-by: Rick Jones <rick.jones2@hp.com> Signed-off-by: David S. Miller <davem@davemloft.net>