From: Jesse Brandeburg <jesse.brandeburg@intel.com>
To: Ben Hutchings <bhutchings@solarflare.com>
Cc: Michael Chan <mchan@broadcom.com>, <davem@davemloft.net>,
<netdev@vger.kernel.org>
Subject: Re: [PATCH 1/3 net-next] bnx2: Add support for ethtool --show-channels|--set-channels
Date: Tue, 7 Feb 2012 17:19:33 -0800 [thread overview]
Message-ID: <20120207171933.00001f12@unknown> (raw)
In-Reply-To: <1328654187.3549.40.camel@bwh-desktop>
On Tue, 7 Feb 2012 22:36:27 +0000
Ben Hutchings <bhutchings@solarflare.com> wrote:
> > > > If I read this correctly, IRQs may be shared between RX and TX queues
> > > > i.e. there may be 'combined channels'.
> > >
> > > It is true that an IRQ can have a TX and a RX queue, but they don't both
> > > have to be enabled. Because of that, it is easier to treat them as
> > > independent queues. They are independent in all aspects except the IRQ.
> >
> > Given that these numbers can be set independently, I can see that
> > treating TX and RX queues as having separate sets of channels might make
> > the set_channels operation easier to understand.
> >
> > The kernel-doc actually committed for struct ethtool_channels is not at
> > all clear on what is meant by a 'channel', but it was certainly my
> > intent that a channel should correspond to one IRQ and the total number
> > of IRQs used by a device would be equal to the sum of
> > {rx,tx,other,combined}_count. Which is certainly not the case for the
> > implementation in bnx2.
>
> It doesn't seem to be true for the original implementation in qlcnic
> either. That has 1 IRQ shared between RX and TX, with additional IRQs
> for RX only, but it reports them as all separate. (It also seems to
> report the number of TX channels to be what the firmware reports as the
> maximum, despite the fact the driver only uses 1.)
>
> There really should be some way to report, and potentially change,
> whether IRQs are shared between RX and TX queues. I wonder if it isn't
> too late to rename and redefine the max_combined and combined_count
> fields...
I'm not very fond of the current ethtool implementation either. Just
today I was implementing the -l/-L options for ixgbe, and since ixgbe
hardware can support 1-all queues on a single interrupt vector, it is
very difficult to express any kind of useful control over anything but
the most basic cases. The driver defaults today to queue tx/rx pairs
per interrupt, with one interrupt per CPU. This default is easy to
express, but if I want to have 1 tx queue per cpu thread, and 1 rx
queue per socket, what do we do then?
While we're at it, can we at least mention in the -h (and man page) that
this is about queues (and or interrupts)? The "channels" reference
ends up being obtuse and difficult for no reason that I can discern.
In my initial interpretation of the data structure I was showing:
Channel parameters for p6p1:
Pre-set maximums:
RX: 64
TX: 64
Other: 0
Combined: 64
Current hardware settings:
RX: 8
TX: 8
Other: 0
Combined: 8
p6p1 /proc/interrupts
p6p1-TxRx-0
p6p1-TxRx-1
p6p1-TxRx-2
p6p1-TxRx-3
p6p1-TxRx-4
p6p1-TxRx-5
p6p1-TxRx-6
p6p1-TxRx-7
p6p1
8 rx queues, 8 tx queues and they were all combined.
prev parent reply other threads:[~2012-02-08 1:19 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-06 1:24 [PATCH 1/3 net-next] bnx2: Add support for ethtool --show-channels|--set-channels Michael Chan
2012-02-06 1:24 ` [PATCH 2/3 net-next] bnx2: Add missing memory barrier in bnx2_start_xmit() Michael Chan
2012-02-06 1:24 ` [PATCH 3/3 net-next] cnic: Add FCoE parity error recovery Michael Chan
2012-02-06 3:46 ` David Miller
2012-02-06 3:46 ` [PATCH 2/3 net-next] bnx2: Add missing memory barrier in bnx2_start_xmit() David Miller
2012-02-06 3:46 ` [PATCH 1/3 net-next] bnx2: Add support for ethtool --show-channels|--set-channels David Miller
2012-02-07 20:19 ` Ben Hutchings
2012-02-07 20:58 ` Michael Chan
2012-02-07 22:01 ` Ben Hutchings
2012-02-07 22:36 ` Ben Hutchings
2012-02-08 1:19 ` Jesse Brandeburg [this message]
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