Date: Thu, 6 Nov 2014 15:04:29 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Ryan Stone <rysto32@gmail.com> Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, "Alexander V. Chernikov" <melifaro@freebsd.org> Subject: Re: svn commit: r273112 - head/sys/dev/ixgbe Message-ID: <CAJ-Vmom5juVfagXxsQ1nvsvi8JPz%2BZzwsYqKMNvSCO=Dwak7LA@mail.gmail.com> In-Reply-To: <CAFMmRNwT-FBU=WGRhuut8COdMwDmLuwpBGCirJzYHMDx0qv7BQ@mail.gmail.com> References: <201410150122.s9F1Mudu083306@svn.freebsd.org> <545B55FA.6070408@FreeBSD.org> <CAJ-VmokhhBiJ%2Buj8yEsfGj4i6FsaBFiZDdYhtFnHgJC3GAokZQ@mail.gmail.com> <CAFMmRNwT-FBU=WGRhuut8COdMwDmLuwpBGCirJzYHMDx0qv7BQ@mail.gmail.com>
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On 6 November 2014 09:58, Ryan Stone <rysto32@gmail.com> wrote:
> On Thu, Nov 6, 2014 at 12:21 PM, Adrian Chadd <adrian@freebsd.org> wrote:
>> Hm, are there any other hardware counters that we can use to see what
>> was dropped?
>
> On the 82599 and later you need to configure the RQSMR register to map
> queue pools to indices and then the QPRDC[i] register will contain the
> number of drops.
Ok.
> Note that the 82598 doesn't support the DROPEN bit in the SRRCTL
> register. There is a separate DROPEN register on the 82598, but I
> have the following worrisome comment in my version of ixgbe:
>
> if (hw->mac.type == ixgbe_mac_82598EB) {
> /*
> * The DROPEN register is intended to allow us to immediately
> * drop packets that cannot be DMA'ed to memory right away to
> * avoid head-of-line blocking. However we have observed that
> * enabling this functionality can lead to situations where a
> * queue will drop every packet destined for it silently, so
> * we instead accept the HOL blocking and disable the immediate
> * dropping
> */
> IXGBE_WRITE_REG(&adapter->hw, IXGBE_DROPEN, 0);
... even if there's ring slots?
-adrian
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