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Date:      Fri, 6 Jul 2018 00:17:39 -0700
From:      "np@FreeBSD.org" <np@FreeBSD.org>
To:        "Eggert, Lars" <lars@netapp.com>
Cc:        "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, Giuseppe Lettieri <g.lettieri@iet.unipi.it>
Subject:   Re: netmap & chelsio
Message-ID:  <20180706071739.GA13401@ox>
In-Reply-To: <0199F257-F9D2-41D0-B4F9-26FBA1607F61@netapp.com>
References:  <94019926-B14F-47AB-8AD9-C01B4A0E199F@netapp.com> <20180705154710.GA3353@ox> <0199F257-F9D2-41D0-B4F9-26FBA1607F61@netapp.com>

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On Fri, Jul 06, 2018 at 06:41:53AM +0000, Eggert, Lars wrote:
> Hi,
> 
> On 2018-7-5, at 17:47, np@FreeBSD.org wrote:
> > Set hw.cxgbe.fl_pktshift=0 in loader.conf to stop the chip from doing
> > this.  See cxgbe(4) for details on the knob.  It's a historic
> > optimization that doesn't seem to matter on modern CPUs, so the driver
> > default should probably be 0 instead of 2.
> 
> thanks, I must have missed this in the man page.
> 
> Looking at this in detail now, I wonder if there are other loader
> settings that should be set for netmap use, such as
> hw.cxgbe.buffer_packing=0 and/or hw.cxgbe.allow_mbufs_in_cluster=0?

The driver uses dedicated tx/rx queues for netmap and those queues use
netmap provided buffers instead of driver allocated mbuf+cluster used by
normal rx queues.  buffer_packing and allow_mbufs_in_cluster are not
applicable to netmap queues.

Regards,
Navdeep



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