linux-kernel - Re: [PATCH net-next v3 08/11] net: ethernet: ti: cpts: move rx timestamp processing to ptp worker only

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Date:   Thu, 26 Mar 2020 13:15:45 +0200
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Richard Cochran <richardcochran@...il.com>
CC:     "David S . Miller" <davem@...emloft.net>,
        Lokesh Vutla <lokeshvutla@...com>,
        Tony Lindgren <tony@...mide.com>, Sekhar Nori <nsekhar@...com>,
        Murali Karicheri <m-karicheri2@...com>,
        netdev <netdev@...r.kernel.org>, <linux-omap@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v3 08/11] net: ethernet: ti: cpts: move rx
 timestamp processing to ptp worker only

Hi Richard

On 24/03/2020 18:54, Richard Cochran wrote:
> On Tue, Mar 24, 2020 at 05:34:34PM +0200, Grygorii Strashko wrote:
>> I tested both ways and kept this version as i'v not seen any degradation,
>> but, of course, i'll redo the test (or may be you can advise what test to run).
> 
> Measure the time delay from when the frame arrives in the stack until
> that frame+RxTimestamp arrives in the application.  I expect the round
> about way via kthread takes longer.
>   
>> My thoughts were - network stack might not immediately deliver packet to the application
> 
> The network stack always delivers the packet, but you artificially
> delay that delivery by calling netif_receive_skb() later on from
> cpts_match_rx_ts().
> 
>> and PTP worker can be tuned (pri and smp_affinity),
> 
> That won't avoid the net softirq.
> 
>> resulted code will be more structured,
> 
> I am afraid people will copy this pattern in new drivers.  It really
> does not make much sense.

I did additional testing and will drop this patch.
Any other comments from you side?

Thank you.

-- 
Best regards,
grygorii