Date: Fri, 27 Mar 2015 10:33:34 -0700 From: hiren panchasara <hiren@strugglingcoder.info> To: freebsd-net@freebsd.org Cc: jfv@freebsd.org, erj@freebsd.org, nitroboost@gmail.com Subject: Re: em(4): difference between missed_packets and rx_overrun Message-ID: <20150327173334.GB39674@strugglingcoder.info> In-Reply-To: <20150326200853.GA19536@strugglingcoder.info> References: <20150326200853.GA19536@strugglingcoder.info>
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--E13BgyNx05feLLmH Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable + jfv, erj from Intel. On 03/26/15 at 01:08P, hiren panchasara wrote: > This is what we are seeing on em(4) 82574L chipset running stable/10: >=20 > dev.em.0.mac_stats.missed_packets: 1441927 > dev.em.0.interrupts.rx_overrun: 153 >=20 > From the datasheet: > http://www.intel.com/content/www/us/en/ethernet-controllers/82574l-gbe-co= ntroller-datasheet.html >=20 > 10.2.7.4 Missed Packets Count - MPC (0x04010; R) > Counts the number of missed packets. Packets are missed when the receive > FIFO has insufficient space to store the incoming packet. This could be > caused because of too few buffers allocated, or because there is > insufficient bandwidth on the IO bus. Events setting this counter > cause RXO, the receiver overrun interrupt, to be set. This register > does not increment if receives are not enabled. >=20 > 10.2.4.1 Interrupt Cause Read Register - ICR (0x000C0; RC/WC) > RXO Receiver Overrun > Set on receive data FIFO overrun. Could be caused either because > there are no available buffers or because PCIe receive bandwidth is > inadequate. >=20 > So, first one is a count and another one is an interrupt. Are these 2 > related? Both seem to be happen when on card FIFO gets full. We see no > evidence of RX queue on the host being full based on > dev.em.0.mac_stats.recv_no_buff. >=20 > Many a times we see missed_packets increasing without rx_overrun > changing. >=20 > The spec says there is a 40KB buffer on card which seems to be used by > both RX and TX? Is is split between them for 20KB each? OR is it > possible that when we are doing high rate TX, we use up that buffer and > RX suffers from that? >=20 > Any insights would be helpful to understand the problem. >=20 > Cheers, > Hiren > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v2.0.22 (FreeBSD) >=20 > iQF8BAEBCgBmBQJVFGdUXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w > ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXRBNEUyMEZBMUQ4Nzg4RjNGMTdFNjZGMDI4 > QjkyNTBFMTU2M0VERkU1AAoJEIuSUOFWPt/l8QoH/3xKvDx9inKcwiPW1authYpw > P/o7TCALanXNp2RyRjSdLnKr1EU4Kv6Twh1qlSun3N9JuxQbVdRCJiF6bAKsdeMm > uvWXFOIOCy1rBbctiVvXUXgPMIEOhywNr7nbdEILV/dFpBMkhGxr9bZPtE7j88cK > 0sX6sO8HLE1b94s/SufMMr/cvJr4m3GbNlSxcq2NjUUKafXJohmVaXfJcp9nXRPz > 148FUCvLL5/DbatzOyg1UQOXItOk2QghIouNcRhd0ls7yTU4BjGDL2z/c/dFOvfM > OV+7jl398uy1k6XnsGDX+TmGunajtIHCPQz4gwV5CJQ0Qq/UqrPs0neBPebUGXo=3D > =3D09Jg > -----END PGP SIGNATURE----- --E13BgyNx05feLLmH Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (FreeBSD) iQF8BAEBCgBmBQJVFZRtXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXRBNEUyMEZBMUQ4Nzg4RjNGMTdFNjZGMDI4 QjkyNTBFMTU2M0VERkU1AAoJEIuSUOFWPt/l/AwIAJf4S+AZkn8axYfhenwtbKUm u55Lw2hJ+ugJHM6OqoxJcbrcJ45WRHW11alNHfVrg+9HUveVWbKeTuWAiJwa3LR1 OhWWeHFPjISL5B93LvxwY+MxNwISxcHe2z9/QHbjSSXw6tnlSbUYS/293/XfdXhK 940dlUhpxq/4RpSOJBkaaqdcMC+gd6KkSeIYom5EB3U1otDDJcOshJAeWtXVCVkj nKteNnXrCEyGAqT1vz92GIAaVXpt7fgC4UM1EpFndqWlLYdWmIKp4N0bOE9h+axG pr5PgCqjjq1w+7jUPPuQ8eK3MQbXvH/lDCIwVvJ9iat3RQ0F7OxYgHB9q0/wKGs= =EZ9H -----END PGP SIGNATURE----- --E13BgyNx05feLLmH--
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