netdev - Re: [PATCH net-next] net/packet: fix TPACKET_V3 performance issue in case of TSO

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Date:   Wed, 25 Mar 2020 10:37:59 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     yang_y_yi@....com
Cc:     Network Development <netdev@...r.kernel.org>, u9012063@...il.com,
        yangyi01@...pur.com
Subject: Re: [PATCH net-next] net/packet: fix TPACKET_V3 performance issue in
 case of TSO

On Wed, Mar 25, 2020 at 10:10 AM <yang_y_yi@....com> wrote:
>
> From: Yi Yang <yangyi01@...pur.com>
>
> TPACKET_V3 performance is very very bad in case of TSO, it is even
> worse than non-TSO case. For Linux kernels which set CONFIG_HZ to
> 1000, req.tp_retire_blk_tov = 1 can help improve it a bit, but some
> Linux distributions set CONFIG_HZ to 250, so req.tp_retire_blk_tov = 1
> actually means req.tp_retire_blk_tov = 4, it won't have any help.
>
> This fix patch can fix the aforementioned performance issue, it can
> boost the performance from 3.05Gbps to 16.9Gbps, a very huge
> improvement. It will retire current block as early as possible in
> case of TSO in order that userspace application can consume it
> in time.
>
> Signed-off-by: Yi Yang <yangyi01@...pur.com>

I'm not convinced that special casing TSO packets is the right solution here.

We should consider converting TPACKET_V3 to hrtimer and allow usec
resolution block timer.

Would that solve your issue?