netdev - Re: [PATCH net-next 2/5] ionic: smaller coalesce default

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Date:   Mon, 31 Aug 2020 21:20:39 -0700
From:   Shannon Nelson <snelson@...sando.io>
To:     David Miller <davem@...emloft.net>, kuba@...nel.org
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next 2/5] ionic: smaller coalesce default

On 8/31/20 5:16 PM, David Miller wrote:
> From: Jakub Kicinski <kuba@...nel.org>
> Date: Mon, 31 Aug 2020 16:50:54 -0700
>
>> On Mon, 31 Aug 2020 16:35:55 -0700 Shannon Nelson wrote:
>>> diff --git a/drivers/net/ethernet/pensando/ionic/ionic_dev.h b/drivers/net/ethernet/pensando/ionic/ionic_dev.h
>>> index 9e2ac2b8a082..2b2eb5f2a0e5 100644
>>> --- a/drivers/net/ethernet/pensando/ionic/ionic_dev.h
>>> +++ b/drivers/net/ethernet/pensando/ionic/ionic_dev.h
>>> @@ -16,7 +16,7 @@
>>>   #define IONIC_DEF_TXRX_DESC		4096
>>>   #define IONIC_LIFS_MAX			1024
>>>   #define IONIC_WATCHDOG_SECS		5
>>> -#define IONIC_ITR_COAL_USEC_DEFAULT	64
>>> +#define IONIC_ITR_COAL_USEC_DEFAULT	8
>> 8 us interrupt coalescing does not hurt general operations?! No way.
>>
>> It's your customers who'll get hurt here, so your call, but I seriously
>> doubt this. Unless the unit is not usec?
> Agreed, 8usec is really really low.  You won't get much coalescing during
> bulk transfers with a value like that, eliminating the gain from coalescing
> in the first place.

Thanks.  I'll drop this patch and come back to this issue when we get a 
chance to add adaptive coalescing.

sln