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Mon, 3 Nov 2025 15:45:24 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id 5A3FjOFU012951 for bugs@FreeBSD.org; Mon, 3 Nov 2025 15:45:24 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 290773] vtnet: Severe performance regression since D51686 Date: Mon, 03 Nov 2025 15:45:24 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: 14.3-STABLE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Only Me X-Bugzilla-Who: lg@efficientip.com X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version rep_platform op_sys bug_status bug_severity priority component assigned_to reporter Message-ID: Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="UTF-8" X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated List-Id: Bug reports List-Archive: https://lists.freebsd.org/archives/freebsd-bugs List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-bugs@FreeBSD.org MIME-Version: 1.0 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.=