netdev - RE: Error 'netif_napi_add_weight() called with weight 256'

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Date: Mon, 14 Aug 2023 07:07:13 +0000
From: Hayes Wang <hayeswang@...ltek.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: "Limonciello, Mario" <mario.limonciello@....com>,
        "edumazet@...gle.com"
	<edumazet@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net"
	<davem@...emloft.net>,
        "linux-usb@...r.kernel.org"
	<linux-usb@...r.kernel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "Paul
 Menzel" <pmenzel@...gen.mpg.de>
Subject: RE: Error 'netif_napi_add_weight() called with weight 256'

Jakub Kicinski <kuba@...nel.org>
> Sent: Thursday, August 10, 2023 2:38 AM
[...]
> High weight will cause higher latency for other softirq and RT
> processing, it's not a good idea. Even with weight/budget of 64
> if there's no higher prio work to do the driver will be polled
> again immediately if it consumed the budget and has more packets.

I mean that only the slow platform uses more than 64 budget,
even I set the weight to 256.
That is, for the fast platform, the actual used budget is always less than 64,
even the weight is 256.

> Do you have some actual data on how the device performs with budget
> of 64 and 256? And maybe perf traces to show where the difference goes?

I tested that slow embedded platform many years ago, so I
don't remember the actual data.
I think the difference is more than 400Mbps.

Best Regards,
Hayes