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

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Message-ID: <b6e63788-b68d-cf7f-807d-6b2651ceff33@gmail.com>
Date:   Sun, 28 Jan 2018 21:35:33 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org
Subject: Re: [Patch net-next v3 0/3] net_sched: reflect tx_queue_len change
 for pfifo_fast

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

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

.John

> ---
> v3: use skb_array_resize_multiple()
> v2: handle error case for ->change_tx_queue_len()
> 
> Cong Wang (3):
>   net: introduce helper dev_change_tx_queue_len()
>   net_sched: plug in qdisc ops change_tx_queue_len
>   net_sched: implement ->change_tx_queue_len() for pfifo_fast
> 
>  include/linux/netdevice.h |  1 +
>  include/net/sch_generic.h |  2 ++
>  net/core/dev.c            | 29 +++++++++++++++++++++++++++
>  net/core/net-sysfs.c      | 25 +----------------------
>  net/core/rtnetlink.c      | 18 +++++------------
>  net/sched/sch_generic.c   | 51 +++++++++++++++++++++++++++++++++++++++++++++++
>  6 files changed, 89 insertions(+), 37 deletions(-)
>