define large activity? large number of files open? large files being transferred? lots of slow clients? This is taken off a machine that runs nginx serving 900+mb/sec of 120k or smaller images on a Quad Core Xeon 2.4. The settings on a server that does streaming content are much different. Each machine config is different based on the requirements. Blindly implementing these could make your performance better or worse.
fs/file-max=60000
fs/dir-notify-enable=0
net/ipv4/tcp_keepalive_time=600
net/core/rmem_max=262143
net/core/rmem_default=262143
net/core/wmem_max=262143
net/core/wmem_default=262143
net/ipv4/tcp_sack=0
net/ipv4/tcp_timestamps=0
net/nf_conntrack_max=262143
net/ipv4/tcp_frto=0
net.ipv4.tcp_sack=1
net.ipv4.tcp_timestamps=1
net.ipv4.tcp_wmem = 4096 65536 4194304
net.ipv4.tcp_rmem = 4096 87380 4194304
net.ipv4.tcp_fin_timeout = 1
net.ipv4.tcp_tw_recycle = 1
net.core.wmem_max = 16777216
net.core.rmem_max = 16777216
net.core.wmem_default = 16777216
net.core.rmem_default = 16777216
net.core.netdev_max_backlog = 262144
net.core.somaxconn = 262144
net.ipv4.tcp_syncookies = 0
net.ipv4.tcp_max_orphans = 262144
net.ipv4.tcp_max_syn_backlog = 262144
net.ipv4.tcp_synack_retries = 2
net.ipv4.tcp_syn_retries = 2
While the information on this page is somewhat old, much of it still applies:
http://www.acc.umu.se/~maswan/linux-netperf.txt
www.ibm.com/developerworks/linux/library/l-hisock.html
slaptijack.com/system-administration/linux-tcp-performance-tuning/