Why Does TCP Send‑Q Grow Beyond SO_SNDBUF? Inside Linux Kernel Buffer Mechanics

This article explains why a TCP connection's Send‑Q can exceed the user‑set SO_SNDBUF value, detailing the kernel's double‑buffer trick, sk_wmem_queued accounting, tcp_sendmsg behavior, GSO influence, and possible ways to limit the buffer growth.

GSOLinux kernelNetworking

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Why Does TCP Send‑Q Grow Beyond SO_SNDBUF? Inside Linux Kernel Buffer Mechanics