bonding: Add tlb_dynamic_lb parameter for tlb mode

The aggresive load balancing causes packet re-ordering as active
flows are moved from a slave to another within the group. Sometime
this aggresive lb is not necessary if the preference is for less
re-ordering. This parameter if used with value "0" disables
this dynamic flow shuffling minimizing packet re-ordering. Of course
the side effect is that it has to live with the static load balancing
that the hashing distribution provides. This impact is less severe if
the correct xmit-hashing-policy is used for the tlb setup.

The default value of the parameter is set to "1" mimicing the earlier
behavior.

Ran the netperf test with 200 stream for 1 min between two hosts with
4x1G trunk (xmit-lb mode with xmit-policy L3+4) before and after these
changes. Following was the command used for those 200 instances -

    netperf -t TCP_RR -l 60 -s 5 -H <host> -- -r81920,81920

Transactions per second:
    Before change: 1,367.11
    After  change: 1,470.65

Change-Id: Ie3f75c77282cf602e83a6e833c6eb164e72a0990
Signed-off-by: Mahesh Bandewar <maheshb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 29 insertions, 0 deletions

diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
index 0e8b268da0a0..431892f1a4ce 100644
--- a/drivers/net/bonding/bond_sysfs.c
+++ b/drivers/net/bonding/bond_sysfs.c
@@ -1039,6 +1039,34 @@ static ssize_t bonding_store_lp_interval(struct device *d,
 static DEVICE_ATTR(lp_interval, S_IRUGO | S_IWUSR,
 		   bonding_show_lp_interval, bonding_store_lp_interval);
 
+static ssize_t bonding_show_tlb_dynamic_lb(struct device *d,
+					   struct device_attribute *attr,
+					   char *buf)
+{
+	struct bonding *bond = to_bond(d);
+	return sprintf(buf, "%d\n", bond->params.tlb_dynamic_lb);
+}
+
+static ssize_t bonding_store_tlb_dynamic_lb(struct device *d,
+					    struct device_attribute *attr,
+					    const char *buf,
+					    size_t count)
+{
+	struct bonding *bond = to_bond(d);
+	int ret;
+
+	ret = bond_opt_tryset_rtnl(bond, BOND_OPT_TLB_DYNAMIC_LB,
+				   (char *)buf);
+	if (!ret)
+		ret = count;
+
+	return ret;
+}
+
+static DEVICE_ATTR(tlb_dynamic_lb, S_IRUGO | S_IWUSR,
+		   bonding_show_tlb_dynamic_lb,
+		   bonding_store_tlb_dynamic_lb);
+
 static ssize_t bonding_show_packets_per_slave(struct device *d,
 					      struct device_attribute *attr,
 					      char *buf)
@@ -1099,6 +1127,7 @@ static struct attribute *per_bond_attrs[] = {
 	&dev_attr_min_links.attr,
 	&dev_attr_lp_interval.attr,
 	&dev_attr_packets_per_slave.attr,
+	&dev_attr_tlb_dynamic_lb.attr,
 	NULL,
 };