Date: Mon, 26 Aug 2013 09:06:38 +0200 From: Harald Schmalzbauer <h.schmalzbauer@omnilan.de> To: freebsd-stable@freebsd.org Subject: if_em, legacy nic and GbE saturation Message-ID: <521AFE7E.2040705@omnilan.de>
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This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigD5E68D27A12A0C935A3A0037 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: quoted-printable Hello, I recycled an older box and put an i350-2 together with a second 82541GI (PCI-slot, one already on-board) into it. The two i350-ports are used with VMDq for ESXi5.1. The two 82541GI are used as lagg-nics by a 9.2-RC (amd64) guest as passthrou PCI device. Always had good results with such setups, but found out, that nics which use the legacy driver part of if_em max out at ~0.6Gbits/s (1500 MTU). There's another NIC on board of this recycle-box, a 82566-PHY (ICH9 integrated MAC). This one uses also if_em, but not legacy code, it reports version 7.3.8 (compared to 1.0.6). And it has no problem fully saturating GbE (~925Mbits/s, no jumbo Frames support anyways). I'm using iperf, with and without lagg (doesn't change anyhing, like it doesn't influence tests on some other boxes with 82576 and i350 (igb)) I see enough idle cycles so CPU shouldn't limit the legacy if_em nics. Also, I see the 82541 consuming arround 8k irqs. Same does the 82566-PHY, but with much higher throughput... I'd like to know if I can't generally expect to saturate older (PCI) GbE nics the line for any reason... I can remember tigeon cards from more than a decade ago, which indeed seemd to lack the performance to gain GbE, but I thought that was no issue shortly later and no "modern" Intel-GbE card had such constraints!? Is there any special tuning for legacy if_em (no need for any TCP tuning, 82566 doesn't have any issue)? Thanks, -Harry --------------enigD5E68D27A12A0C935A3A0037 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (FreeBSD) iEYEARECAAYFAlIa/oMACgkQLDqVQ9VXb8hOGgCgpr/IGqH1zfmwOUuAMMA3bJXT 1J8AnRzwq89uWdIEUC5krugJEU8V645k =sDBx -----END PGP SIGNATURE----- --------------enigD5E68D27A12A0C935A3A0037--
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