Re: [PATCH] net: bonding: Fix transmit load balancing in balance-alb mode if specified by sysfs

On Thu, Sep 7, 2017 at 5:39 PM, Mahesh Bandewar (महेश बंडेवार)
[off-list ref] wrote:

On Thu, Sep 7, 2017 at 4:09 PM, Nikolay Aleksandrov
[off-list ref] wrote:

quoted

On  7.09.2017 01:47, Kosuke Tatsukawa wrote:

quoted

Commit cbf5ecb30560 ("net: bonding: Fix transmit load balancing in
balance-alb mode") tried to fix transmit dynamic load balancing in
balance-alb mode, which wasn't working after commit 8b426dc54cf4
("bonding: remove hardcoded value").

It turned out that my previous patch only fixed the case when
balance-alb was specified as bonding module parameter, and not when
balance-alb mode was set using /sys/class/net/*/bonding/mode (the most
common usage).  In the latter case, tlb_dynamic_lb was set up according
to the default mode of the bonding interface, which happens to be
balance-rr.

This additional patch addresses this issue by setting up tlb_dynamic_lb
to 1 if "mode" is set to balance-alb through the sysfs interface.

I didn't add code to change tlb_balance_lb back to the default value for
other modes, because "mode" is usually set up only once during
initialization, and it's not worthwhile to change the static variable
bonding_defaults in bond_main.c to a global variable just for this
purpose.

Commit 8b426dc54cf4 also changes the value of tlb_dynamic_lb for
balance-tlb mode if it is set up using the sysfs interface.  I didn't
change that behavior, because the value of tlb_balance_lb can be changed
using the sysfs interface for balance-tlb, and I didn't like changing
the default value back and forth for balance-tlb.

As for balance-alb, /sys/class/net/*/bonding/tlb_balance_lb cannot be
written to.  However, I think balance-alb with tlb_dynamic_lb set to 0
is not an intended usage, so there is little use making it writable at
this moment.

Fixes: 8b426dc54cf4 ("bonding: remove hardcoded value")

This is wrong! I think you are confusing various things here. ALB is
different mode from TLB and TLB-dynamic-lb is *only* a special case of
TLB. Your earlier patch is also wrong for the same reasons. However,
since the default value of tlb_dynamic_lb is set to 0  it's not
causing issues for ALB mode otherwise it would break ALB mode.

I take this back. The default value is 1 so ALB is broken because of
the referenced change.

tlb_dynamic_lb has absolutely nothing to do with ALB mode. Please
revert the earlier change (cbf5ecb30560).

It's not clear to me what you saw as broken, so can't really suggest
what really need to be done.