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Date:      Fri, 06 Apr 2018 19:56:33 +0000
From:      bugzilla-noreply@freebsd.org
To:        virtualization@FreeBSD.org
Subject:   [Bug 215737] [bhyve] utilizing virtio-net truncates jumbo frames at 4084 bytes length
Message-ID:  <bug-215737-27103-nPEabsgQLz@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-215737-27103@https.bugs.freebsd.org/bugzilla/>
References:  <bug-215737-27103@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D215737

--- Comment #13 from Harald Schmalzbauer <bugzilla.freebsd@omnilan.de> ---
(In reply to P Kern from comment #12)

In case you end up switching from "vmxnet3"/[vmx(4)|vmx3f(4)] to
"e1000"/[em(4)], depending on your workload, you can save lots of overhead =
if
you switch to "e1000e" instead, since it utilizes MSI(-X).
To make use of, you need to set 'hw.pci.honor_msi_blacklist=3D0' in loader.=
conf.

And then, there's a negotiaten mismatch between FreeBSD/ESXi (ESX is select=
ing
MSI while FreeBSD MSI-X =E2=80=93 as far as I remember).  You can circumven=
t by simply
re-loading the kernel module!  "e1000e"/[if_em(4)] works fine in MSI-X mode.

Since FreeBSD-11, there's also devctl(8), which could take care of the driv=
er
re-initialization, but when I wrote my rc(8) script to automatically re-load
kernel modules on ESXi guests, it was not available.
Happy to share the rc(8) script on request.

-harry

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