Date: Mon, 03 Nov 2025 15:45:24 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 290773] vtnet: Severe performance regression since D51686 Message-ID: <bug-290773-227@https.bugs.freebsd.org/bugzilla/>
next in thread | raw e-mail | index | archive | help
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D290773 Bug ID: 290773 Summary: vtnet: Severe performance regression since D51686 Product: Base System Version: 14.3-STABLE Hardware: amd64 OS: Any Status: New Severity: Affects Only Me Priority: --- Component: kern Assignee: bugs@FreeBSD.org Reporter: lg@efficientip.com Hello, I am experiencing a severe network performance regression on KVM-based environments (like GCE and Proxmox) using vtnet (VirtIO) network interfaces. Symptoms: Network throughput (e.g., during an scp transfer) collapses to extremely low speeds (approx. 3-4 KB/s). The guest VM is not overloaded (CPU remains idle). Root Cause (Specific Commit): This regression was introduced by commit: a98b5f3ff34e7ff851f6127a64ebd88818c8d004 If I revert this single commit, network performance returns to normal, even with TSO enabled. Workaround (Confirms TSO issue): The issue is directly related to TCP Segmentation Offload (TSO). Disabling TSO manually on the interface also resolves the performance problem: ifconfig vtnet0 -tso Steps to Reproduce: Run a 14-STABLE kernel containing commit a98b5f3ff34e. Host the VM on a KVM hypervisor. Attempt to transfer a file from the VM using scp from another host. Observe throughput drop to near-zero. --=20 You are receiving this mail because: You are the assignee for the bug.=
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?bug-290773-227>