にゃんかもうデフォルト値がおかしいとしか思えにゃいんだが、暫定でデカい目の数値つっこんどけ的トラブル回避で以下のようにゃ設定に。
net.core.rmem_max = 8388608
net.core.rmem_default = 8388608
net.core.wmem_max = 8388608
net.core.wmem_default = 8388608
net.core.optmem_max = 8388608
net.ipv4.tcp_rmem = 4096 87380 8388608
net.ipv4.tcp_wmem = 4096 87380 8388608
net.ipv4.neigh.default.gc_thresh3 = 65536
net.ipv4.neigh.default.gc_thresh2 = 8192
net.ipv4.neigh.default.gc_thresh1 = 1024
net.core.netdev_max_backlog = 25000
net.ipv4.tcp_mem = 46944 62592 8388608
kernel.shmall = 33554432
kernel.shmmax = 33554432