Most popular speedup sysctl options for Proxmox. Put in /etc/sysctl.d/

sysctl-proxmox-tune.conf

# allow that much active connections
net.core.somaxconn = 256000

# do less swap but not disable it
vm.swappiness = 1

# allow application request allocation of virtual memory
# more than real RAM size (or OpenVZ/LXC limits)
vm.overcommit_memory = 1

net.core.netdev_max_backlog = 16000
net.ipv4.tcp_max_syn_backlog = 32000
net.ipv4.tcp_syncookies = 1

net.unix.max_dgram_qlen = 1024

# Don't need IPv6 for now
# If you use IPv6 - comment this line
net.ipv6.conf.all.disable_ipv6 = 1

# Flush TIME_WAIT connections faster
net.ipv4.tcp_fin_timeout = 10
# same for nf_conntrac moule
net.netfilter.nf_conntrack_tcp_timeout_fin_wait = 15

# Increase ephermeral IP ports
net.ipv4.ip_local_port_range = 10240    61000

# https://www.serveradminblog.com/2011/02/neighbour-table-overflow-sysctl-conf-tunning/
net.ipv4.neigh.default.gc_thresh1 = 1024
net.ipv4.neigh.default.gc_thresh2 = 2048
net.ipv4.neigh.default.gc_thresh3 = 4096

# http://www.opennet.ru/opennews/art.shtml?num=44945
net.ipv4.tcp_challenge_ack_limit = 9999

# https://major.io/2008/12/03/reducing-inode-and-dentry-caches-to-keep-oom-killer-at-bay/
vm.vfs_cache_pressure = 10000

##
# Adjust vfs cache
# https://lonesysadmin.net/2013/12/22/better-linux-disk-caching-performance-vm-dirty_ratio/
# Decriase dirty cache to faster flush on disk
vm.dirty_background_ratio = 5
vm.dirty_ratio = 10
# Only on Proxmox 3.x with OpenVZ
ubc.dirty_ratio = 20
ubc.dirty_background_ratio = 10

# Don't slow network - save congestion window after idle
# https://github.com/ton31337/tools/wiki/tcp_slow_start_after_idle---tcp_no_metrics_save-performance
net.ipv4.tcp_slow_start_after_idle = 0

# https://tweaked.io/guide/kernel/
# Don't migrate processes between CPU cores too often
kernel.sched_migration_cost_ns = 5000000
# Kernel >= 2.6.38 (ie Proxmox 4+)
kernel.sched_autogroup_enabled = 0