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Date:      Tue, 15 Sep 2015 11:40:27 -0700
From:      Adrian Chadd <adrian.chadd@gmail.com>
To:        Hans Petter Selasky <hps@selasky.org>
Cc:        =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= <royger@freebsd.org>,  "src-committers@freebsd.org" <src-committers@freebsd.org>,  "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>,  "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>
Subject:   Re: svn commit: r271946 - in head/sys: dev/oce dev/vmware/vmxnet3 dev/xen/netfront kern net netinet ofed/drivers/net/mlx4 sys
Message-ID:  <CAJ-Vmo=J7-bM_kV0PD2%2BiWqBLLi24S4KjubuExOhn26j62zr9A@mail.gmail.com>
In-Reply-To: <55F864C2.9030102@selasky.org>
References:  <201409220827.s8M8RRHB031526@svn.freebsd.org> <55F69093.5050807@FreeBSD.org> <55F6935C.9000000@selasky.org> <55F6A694.7020404@FreeBSD.org> <55F6A914.6050109@selasky.org> <55F6ED8F.5030402@FreeBSD.org> <CAJ-Vmo=vq6NbUNecTvkzDLQW3rQzpPToFGbR9TxdcyO_BL3s_g@mail.gmail.com> <55F7FE1A.3050500@selasky.org> <CAJ-VmonsGdG9eddWLLPTG3wwW3FDHDkH-F2xD%2B2nt=yvwBRS-A@mail.gmail.com> <55F864C2.9030102@selasky.org>

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On 15 September 2015 at 11:34, Hans Petter Selasky <hps@selasky.org> wrote:
> Hi Adrian,
>
> On 09/15/15 19:13, Adrian Chadd wrote:
>>
>> I know all of this. What I'm asking is different - what about the
>> change(s) that broke/fixed the Xen network performance actually caused
>> the change in behaviour? I know things are sensitive to how the mbufs
>> are broken up - I'd like to see exactly this.
>
>
> You need to add statistic counters to the network drivers in question, how
> frequently packets are defragged and/or dropped in the TX path to figure
> that out. Can we continue this discussion elsewhere?

Sure thing.

Yes, maybe having a per-interface histogram of mbuf / segment sizes
would be good - something we can run live on a box rather than trying
to use dtrace. I wonder how difficult it'd be to slip something in as
part of if_transmit and ifnet..



-adrian



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