Date: Wed, 21 Nov 2012 16:40:42 +0000 From: John Fretby <jfretby@googlemail.com> To: Victor Balada Diaz <victor@bsdes.net> Cc: freebsd-isp@freebsd.org Subject: Re: FreeBSD boxes as a 'router'... Message-ID: <CAN9kdQm_1NAkPPOjsbwRXoHMEMc81b%2B6EXoaHH99uv0dG%2B56Ng@mail.gmail.com> In-Reply-To: <20121121145758.GD50873@equilibrium.bsdes.net> References: <CAN9kdQnkaF3NdEsoBh2q%2Bxf73rur%2B1JSVGcUo8xfhugJMQ_oMw@mail.gmail.com> <20121120174554.GC50873@equilibrium.bsdes.net> <CAN9kdQmZhsOKmgB0hns_f8ENcpUauLocBX6-VXDqE_2D8EdKzA@mail.gmail.com> <20121121145758.GD50873@equilibrium.bsdes.net>
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On 21 November 2012 14:57, Victor Balada Diaz <victor@bsdes.net> wrote: > I think you forgot to CC the list. I'll add it so you can get > more answers. > I did forget, thanks for that! :) > em(4) and igb(4) are both drivers for Intel NICs. They just have > different capabilities. The sysctl you're asking for controls behavior > of adaptive interrupt moderation. It's a recommended tuning for end hosts > more than routers. You can read more about interrupt moderation on this > document: > > http://www.intel.com/design/network/applnots/ap450.htm > > em(4) NICs don't have all the capabilities of igb(4) ones. Some em(4) NICs > have > interrupt moderation (eg: 82574L) but not all of them do. If your em(4) > card does > have interrupt moderation you can tune it with: > > hw.em.rx_int_delay > hw.em.rx_abs_int_delay > hw.em.tx_int_delay > hw.em.tx_abs_int_delay > > Exchanging latency to get more throughput. > > You can take a look at this document explaining capabilities of different > NICs: > > > http://www.intel.com/content/dam/doc/brochure/ethernet-controllers-phys-brochure.pdf > > You should ask supermicro what's the exact model they'll put on your server > and then decide if it's OK for you. They are apparently: em0: <Intel(R) PRO/1000 Network Connection 7.3.2> port 0xf020-0xf03f mem 0xdfa00000-0xdfa1ffff,0xdfa25000-0xdfa25fff irq 20 at device 25.0 on pci0 em0: Using an MSI interrupt ... em0: flags=8c02<BROADCAST,OACTIVE,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=4219b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,WOL_MAGIC,VLAN_HWTSO> > About the interrupt storm: We've had various interrupt storms that were > caused by > different problems. The most common was a software bug with interrupts. > After > reporting on the lists it was fixed and we didn't have problems again. > > If you have a problem with high interrupts because too many small packets > (eg a DoS), > getting a card with interrupt moderation should help a lot. Most probably > your problem > with interrupt storms was caused by something else like a shared interrupt > with other > device or software bug. Without more analysis it's impossible to really > say. > I have some details from when it happened - it doesn't look like it was a shared interrupt issue - it just literally looks like the host came up, with a stampeding hurd of "other" hosts hitting it for services that weren't yet running, and it folded :( That's why I was wondering if there was a similar sysctl for the em driver - in order to raise the number of interrupts the system allows, before declaring it "a storm". > > Keep in mind that i'm not an expert on this area, so you might get better > answers > on frebsd-net@ :) > > Hope it helps. > It has - half the problem is there are *so* many options, combinations - and no matter what you pick, if you look them up enough you'll find someone finding fault with them, or casting doubts on their performance. Doesn't really help when all you want is something that has a good chance of "working" :) -Jon
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