Date: Mon, 9 Mar 2015 03:34:15 +0000 From: Wei Hu <weh@microsoft.com> To: Adrian Chadd <adrian@freebsd.org> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, Luigi Rizzo <rizzo@iet.unipi.it> Subject: RE: Network interrupt and NAPI in FreeBSD? Message-ID: <BY1PR0301MB0902101A66C146C335701DE5BB1B0@BY1PR0301MB0902.namprd03.prod.outlook.com> In-Reply-To: <CAJ-Vmon3iwTyvVGdOS42G3OSRAs8bwi7NcUDonmcN64xEcwDGw@mail.gmail.com> References: <BY1PR0301MB0902C944E2287E0C6B5D8287BB1C0@BY1PR0301MB0902.namprd03.prod.outlook.com> <CA%2BhQ2%2Bi6d_tsqKpkYVh2jnVQaS4TZ5X7zyh_54ZecQDjm%2BFkRA@mail.gmail.com> <BY1PR0301MB09024C00FF371C7B9E57711EBB1D0@BY1PR0301MB0902.namprd03.prod.outlook.com> <CAJ-Vmon3iwTyvVGdOS42G3OSRAs8bwi7NcUDonmcN64xEcwDGw@mail.gmail.com>
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> -----Original Message----- > From: adrian.chadd@gmail.com [mailto:adrian.chadd@gmail.com] On Behalf > Of Adrian Chadd > Sent: Saturday, March 7, 2015 4:27 PM > To: Wei Hu > Cc: Luigi Rizzo; freebsd-net@freebsd.org > Subject: Re: Network interrupt and NAPI in FreeBSD? > > Hi, > > Well, hm. What's generating the interrupts? How many interrupts/second > are you talking about here? > > People have asked about a NAPI style solution for FreeBSD for a while, but > for most folk that are using one physical interface that does interrupt > moderation/rate-limiting, it turns out to not be all that big a benefit. For > boxes that haves multiple interfaces, or for VMs whose software interrupt > path doesn't implement any kind of thresholds for interrupt moderation, it > still can be a benefit. > > So maybe try looking at making your driver support POLLING and see what > happens. > > Maybe virtualisation will be the straw that breaks the NAPI back for > FreeBSD. ;) > I haven't got chance to measure the interrupt/second rate. What I have seen is when running the same iperf test, the vCPU handle the network queue is over 80% busy running in interrupt context on FreeBSD, comparing to around 15% busy in interrupt context on Linux. The throughput is around 2.0 Gbps vs 3.0 Gbps. I am using a slightly new netvsc driver with TSO support. It hasn't not been officially out yet. Wei
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