netdev - Re: [net-next 01/10] igb: reduce CPU0 latency when updating statistics

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Message-ID: <20181225154715.GA20609@splinter.mtl.com>
Date:   Tue, 25 Dec 2018 17:47:15 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, nhorman@...hat.com,
        sassmann@...hat.com,
        Bernhard Kaindl <bernhard.kaindl@...lesgroup.com>,
        Jan Jablonsky <jan.jablonsky@...lesgroup.com>
Subject: Re: [net-next 01/10] igb: reduce CPU0 latency when updating
 statistics

On Thu, Dec 20, 2018 at 12:56:25PM -0800, Jeff Kirsher wrote:
> This change is based off of the work and suggestion of Jan Jablonsky
> <jan.jablonsky@...lesgroup.com>.
> 
> The Watchdog workqueue in igb driver is scheduled every 2s for each
> network interface. That includes updating a statistics protected by
> spinlock. Function igb_update_stats in this case will be protected
> against preemption. According to number of a statistics registers
> (cca 60), processing this function might cause additional cpu load
>  on CPU0.
> 
> In case of statistics spinlock may be replaced with mutex, which
> reduce latency on CPU0.
> 
> CC: Bernhard Kaindl  <bernhard.kaindl@...lesgroup.com>
> CC: Jan Jablonsky <jan.jablonsky@...lesgroup.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> Tested-by: Aaron Brown <aaron.f.brown@...el.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>

Hi,

I'm hitting following issue with this commit:
https://lists.01.org/pipermail/lkp/2018-September/009139.html