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authorEric Dumazet <eric.dumazet@gmail.com>2011-11-28 22:41:47 +0000
committerDavid S. Miller <davem@davemloft.net>2011-11-29 13:17:03 -0500
commitf07d960df33c5aef8f513efce0fd201f962f94a1 (patch)
tree33f1313283e85a642f4126029e47e4ec1f606282 /net/sched
parent4d77d2b567ec66a443792d99e96ac760991d80d0 (diff)
tcp: avoid frag allocation for small frames
tcp_sendmsg() uses select_size() helper to choose skb head size when a new skb must be allocated. If GSO is enabled for the socket, current strategy is to force all payload data to be outside of headroom, in PAGE fragments. This strategy is not welcome for small packets, wasting memory. Experiments show that best results are obtained when using 2048 bytes for skb head (This includes the skb overhead and various headers) This patch provides better len/truesize ratios for packets sent to loopback device, and reduce memory needs for in-flight loopback packets, particularly on arches with big pages. If a sender sends many 1-byte packets to an unresponsive application, receiver rmem_alloc will grow faster and will stop queuing these packets sooner, or will collapse its receive queue to free excess memory. netperf -t TCP_RR results are improved by ~4 %, and many workloads are improved as well (tbench, mysql...) Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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