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Date:      Tue, 25 Jun 2019 10:21:03 +0200
From:      Roger Pau =?utf-8?B?TW9ubsOp?= <roger.pau@citrix.com>
To:        Christian M <christian.marcos@gmail.com>
Cc:        <freebsd-xen@freebsd.org>
Subject:   Re: Very slow and inconsistent internal network speed (between, VM's on the same host) for FreeBSD 11.0+ as guest on, XCP-ng/XenServer
Message-ID:  <20190625082103.qiiz2cikrauaqlas@MacBook-Air-de-Roger.local>
In-Reply-To: <CAKwR994kQTRfB0R0_WiTYx4pgOHtR-ge7h0vP8NiM_%2B-MBPGGw@mail.gmail.com>
References:  <mailman.7.1560945600.15387.freebsd-xen@freebsd.org> <12994df1-f847-ec92-aae8-43a32e59385f@darco.dk> <CAKwR994kQTRfB0R0_WiTYx4pgOHtR-ge7h0vP8NiM_%2B-MBPGGw@mail.gmail.com>

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On Mon, Jun 24, 2019 at 10:24:09PM +0200, Christian M wrote:
> Thanks for your input Bjarne.
> 
> Previously I tested with iperf2, but I have made som tests with iperf3 now
> also and noticed there are a lot of "Retr" (TCP retries) in some cases.
> Went back here to your post and saw that your results also showed a lot of
> retries in some cases. My new tests showed similar results to yours
> (although not nearly as hi throughput as you have). When Linux is client
> the retries are 0, with FreeBSD as client the number is > 0.

Can you figure out what caused those retries? Wrong MTU, bad
checksums?

> I'm not sure
> if our numbers are considered high though, and something that actually is a
> problem? Although, on a internal network with no external factors like
> interference, I feel this should always be 0 no matter what?

If properly configured yes, there should be no retries when doing
intra-VM connections.

Thanks, Roger.



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