netdev - Re: [Patch net-next v3 0/3] net_sched: reflect tx_queue_len change for pfifo

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Message-ID: <CAM_iQpUPGhnipr+fuwwEBuddz1S1LjJC=gzNao+yte3_wG9usQ@mail.gmail.com>
Date:   Sun, 28 Jan 2018 21:57:11 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [Patch net-next v3 0/3] net_sched: reflect tx_queue_len change
 for pfifo_fast

On Sun, Jan 28, 2018 at 9:35 PM, John Fastabend
<john.fastabend@...il.com> wrote:
> On 01/25/2018 06:26 PM, Cong Wang wrote:
>> This pathcset restores the pfifo_fast qdisc behavior of dropping
>> packets based on latest dev->tx_queue_len. Patch 1 introduces
>> a helper, patch 2 introduces a new Qdisc ops which is called when
>> we modify tx_queue_len, patch 3 implements this ops for pfifo_fast.
>>
>> Please see each patch for details.
>>
>
> Overall this series is better than what we have at the moment, but
> a better fix would preallocate the memory, to avoid ENOMEM errors,

I am not against for better ENOMEM error handling, but I still have to
remind you that attach_one_default_qdisc() doesn't handle it either.
Since no one complained about it, why this one is so special?


> and add a ptr_ring API to use the preallocated buffers.


What ptr_ring API could cure netdev tx queues problem here?
Looks like you still don't understand the problem here.


>
> We have time (its only in net-next) so lets do the complete fix
> rather than this series IMO.
>

Why not just accept this and complete the error handling later
given the fact that I already add a TODO? IOW, why it is now?