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

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Message-ID: <CAF2d9jhxrpmTEqHtf6NES4LmoT8A5O1v==8NJZcDGhS-PS5AFQ@mail.gmail.com>
Date:   Thu, 7 Sep 2017 17:39:36 -0700
From:   Mahesh Bandewar (महेश बंडेवार) 
        <maheshb@...gle.com>
To:     Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Cc:     Kosuke Tatsukawa <tatsu@...jp.nec.com>,
        Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Reinis Rozitis <r@...e.lv>
Subject: Re: [PATCH] net: bonding: Fix transmit load balancing in balance-alb
 mode if specified by sysfs

On Thu, Sep 7, 2017 at 4:09 PM, Nikolay Aleksandrov
<nikolay@...ulusnetworks.com> wrote:
> On  7.09.2017 01:47, Kosuke Tatsukawa wrote:
>> 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.
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.