I'm digging one issue(not sure if it's an issue and not sure how to
fix this) with linux tcp stack. Our application receives a big number
of small packets. Total network utilization isn't really big (dozens
of Mbit/s). Platform: ubuntu 24, ENA-enabled AWS VM.
I observe tcp_send_ack takes half of the whole 'recvfrom' cpu time
(with callstacks to AWS ENA driver). Total recvfrom syscall takes
approx 8.8% and tcp_send_ack is about 5% of the whole profile.
I tried to extend the sockets buffer with proper sysctl's
(net.ipv4.tcp_wmem/net.ipv4.tcp_rmem) and got some improvements.
Nevertheless, I still can't understand how to send ACKs less
frequently and reduce CPU consumption and latency here.
I've found the TCP_QUICKACK socket flag. According to man pages,
disabling this flag will do exactly I need. Will it fix my issue with
manu ACKs?
Is there any ideas or advice on what to do and how to fix such an issue?
