Subject: Re: [PATCH net-next] bond: add support to read speed and duplex via ethtool

From: Jay Vosburgh <[email-masked]>
Date: Wed, 06 Mar 2013 13:46:13 -0800

Andy Gospodarek <[email-masked]> wrote:

>On Wed, Mar 06, 2013 at 11:25:12AM -0800, Jay Vosburgh wrote:
>> Andy Gospodarek <[email-masked]> wrote:
>> 
>> >This patch adds support for the get_settings ethtool op to the bonding
>> >driver.  This was motivated by users who wanted to get the speed of the
>> >bond and compare that against throughput to understand utilization.
>> >The behavior before this patch was added was problematic when computing
>> >line utilization after trying to get link-speed and throughput via SNMP.
>> >
>> >The general plan for computing link-speed was as follows:
>> >
>> >Mode                 Formula
>> >----                 -------
>> >active-backup        speed of current active slave
>> >broadcast            speed of first slave with known speed
>> >all other modes      aggregate speed of all slaves with known speed
>> 
>> 	I'll just point out that the balance-tlb mode is asymmetric; it
>> uses all slaves for transmission, but only one slave for reception.
>> Ethtool only has a single speed for both directions, so this is probably
>> the best choice, but it should still be noted.
>
>Thanks for pointing that out.  I have a feeling there will be a v2, so
>I'll try and update the changelog to reflect that.  For the record, this
>same limitation exists when connecting to most switches and using
>round-robin, so I didn't feel the need to differentiate possibly
>asymmetric speeds.
>
>> >Output from ethtool looks like this for a round-robin bond:
>> >
>> >Settings for bond0:
>> >	Supported ports: [ ]
>> >	Supported link modes:   Not reported
>> >	Supported pause frame use: No
>> >	Supports auto-negotiation: No
>> >	Advertised link modes:  Not reported
>> >	Advertised pause frame use: No
>> >	Advertised auto-negotiation: No
>> >	Speed: 11000Mb/s
>> >	Duplex: Full
>> >	Port: Twisted Pair
>> >	PHYAD: 0
>> >	Transceiver: internal
>> >	Auto-negotiation: off
>> >	MDI-X: Unknown
>> >	Link detected: yes
>> >
>> >I tested this and verified it works as expected.  A test was also done
>> >on a version backported to an older kernel and it worked well there.
>> >
>> >Signed-off-by: Andy Gospodarek <[email-masked]>
>> >---
>> > drivers/net/bonding/bond_main.c | 47 +++++++++++++++++++++++++++++++++++++++++
>> > 1 file changed, 47 insertions(+)
>> >
>> >diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>> >index 7bd068a..6e70ff0 100644
>> >--- a/drivers/net/bonding/bond_main.c
>> >+++ b/drivers/net/bonding/bond_main.c
>> >@@ -4224,6 +4224,52 @@ void bond_set_mode_ops(struct bonding *bond, int mode)
>> > 	}
>> > }
>> >
>> >+static int bond_ethtool_get_settings(struct net_device *bond_dev,
>> >+				     struct ethtool_cmd *ecmd)
>> >+{
>> >+	struct bonding *bond = netdev_priv(bond_dev);
>> >+	struct slave *slave;
>> >+	int i;
>> >+	unsigned long speed = 0;
>> >+
>> >+	ecmd->speed = SPEED_UNKNOWN;
>> >+	ecmd->duplex = DUPLEX_UNKNOWN;
>> >+
>> >+	read_lock(&bond->lock);
>> >+	switch (bond->params.mode) {
>> >+	case BOND_MODE_ACTIVEBACKUP:
>> >+		read_lock(&bond->curr_slave_lock);
>> >+		if (bond->curr_active_slave &&
>> >+		    bond->curr_active_slave->speed != SPEED_UNKNOWN) {
>> >+			ecmd->speed = bond->curr_active_slave->speed;
>> >+			ecmd->duplex = bond->curr_active_slave->duplex;
>> >+		}
>> >+		read_unlock(&bond->curr_slave_lock);
>> >+		break;
>> >+	case BOND_MODE_BROADCAST:
>> >+		bond_for_each_slave(bond, slave, i) {
>> >+			if (slave->speed != SPEED_UNKNOWN) {
>> >+				ecmd->speed = slave->speed;
>> >+				ecmd->duplex = slave->duplex;
>> >+				break;
>> >+			}
>> >+		}
>> >+		break;
>> 
>> 	Does anybody really use broadcast mode?  Not that I'm saying
>> this is incorrect, I'm just wondering in general.
>> 
>
>I don't imagine they do, but wanted to add something for it since it
>would not reallyu fall into the default case well.
>
>> >+	default:
>> >+		bond_for_each_slave(bond, slave, i) {
>> >+			if (slave->speed != SPEED_UNKNOWN) {
>> >+				speed += slave->speed;
>> >+			}
>> >+			if (ecmd->duplex == DUPLEX_UNKNOWN &&
>> >+			    slave->duplex != DUPLEX_UNKNOWN)
>> >+				ecmd->duplex = slave->duplex;
>> 
>> 	Should the calculations skip slaves that are not BOND_LINK_UP?
>> If the ARP monitor is running, some slaves may be carrier up (and have
>> slave->speed set), but are not actually in use by the bond, at least for
>> transmission.
>> 
>
>That would be fine with me.  If you would like I can add that for a v2.
>It would produce a more honest estimate of what the maximum throughput
>would be at that point in time.

	Yes, I think so; it's going to be an estimate for any of the
load balance modes, but it ought to be as close as is reasonable to what
kind of throughput would be expected.

	I also think it might be odd if it were possible for a bond to
simultaneously show as carrier down, but speed as something very high.

	-J

>> >+		}
>> >+		ecmd->speed = speed;
>> >+	}
>> >+	read_unlock(&bond->lock);
>> >+	return 0;
>> >+}
>> >+
>> > static void bond_ethtool_get_drvinfo(struct net_device *bond_dev,
>> > 				     struct ethtool_drvinfo *drvinfo)
>> > {
>> >@@ -4235,6 +4281,7 @@ static void bond_ethtool_get_drvinfo(struct net_device *bond_dev,
>> >
>> > static const struct ethtool_ops bond_ethtool_ops = {
>> > 	.get_drvinfo		= bond_ethtool_get_drvinfo,
>> >+	.get_settings		= bond_ethtool_get_settings,
>> > 	.get_link		= ethtool_op_get_link,
>> > };
>> >
>> >-- 
>> >1.7.11.7
>> 
>> ---
>> 	-Jay Vosburgh, IBM Linux Technology Center, [email-masked]
>> 
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