netdev - 答复: [vger.kernel.org代发]Re: [PATCH net-next] net/packet: fix TPACKET

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Date:   Thu, 26 Mar 2020 00:43:33 +0000
From:   Yi Yang (杨燚)-云服务集团 
        <yangyi01@...pur.com>
To:     "willemdebruijn.kernel@...il.com" <willemdebruijn.kernel@...il.com>,
        "yang_y_yi@....com" <yang_y_yi@....com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "u9012063@...il.com" <u9012063@...il.com>
Subject: 答复: [vger.kernel.org代发]Re: [PATCH net-next] net/packet: fix TPACKET_V3 performance issue in case of TSO

By the way, even if we used hrtimer, it can't ensure so high performance improvement, the reason is every frame has different size, you can't know how many microseconds one frame will be available, early timer firing will be an unnecessary waste, late timer firing will reduce performance, so I still think the way this patch used is best so far.

-----邮件原件-----
发件人: netdev-owner@...r.kernel.org [mailto:netdev-owner@...r.kernel.org] 代表 Willem de Bruijn
发送时间: 2020年3月25日 22:38
收件人: yang_y_yi@....com
抄送: Network Development <netdev@...r.kernel.org>; u9012063@...il.com; Yi Yang (杨燚)-云服务集团 <yangyi01@...pur.com>
主题: [vger.kernel.org代发]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?

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