From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [PATCH net] r8169: fix NAPI handling under high load
Date: Tue, 16 Oct 2018 15:17:08 -0700
Message-ID: <20181016151708.3fff9bd9@xeon-e3>
References: <8f84fe39-3d8d-396d-3b97-027e0a83f8cb@gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Cc: David Miller <davem@davemloft.net>,
        Realtek linux nic maintainers <nic_swsd@realtek.com>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>
To: Heiner Kallweit <hkallweit1@gmail.com>
Return-path: <netdev-owner@vger.kernel.org>
Received: from mail-pg1-f196.google.com ([209.85.215.196]:40654 "EHLO
        mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1726048AbeJQGJi (ORCPT
        <rfc822;netdev@vger.kernel.org>); Wed, 17 Oct 2018 02:09:38 -0400
Received: by mail-pg1-f196.google.com with SMTP id n31-v6so11503402pgm.7
        for <netdev@vger.kernel.org>; Tue, 16 Oct 2018 15:17:10 -0700 (PDT)
In-Reply-To: <8f84fe39-3d8d-396d-3b97-027e0a83f8cb@gmail.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On Tue, 16 Oct 2018 22:37:31 +0200
Heiner Kallweit <hkallweit1@gmail.com> wrote:

> rtl_rx() and rtl_tx() are called only if the respective bits are set
> in the interrupt status register. Under high load NAPI may not be
> able to process all data (work_done == budget) and it will schedule
> subsequent calls to the poll callback.
> rtl_ack_events() however resets the bits in the interrupt status
> register, therefore subsequent calls to rtl8169_poll() won't call
> rtl_rx() and rtl_tx() - chip interrupts are still disabled.
> 
> Fix this by calling rtl_rx() and rtl_tx() independent of the bits
> set in the interrupt status register. Both functions will detect
> if there's nothing to do for them.
> 
> This issue has been there more or less forever (at least it exists in
> 3.16 already), so I can't provide a "Fixes" tag. 
> 
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>

Another issue is this:

	if (work_done < budget) {
		napi_complete_done(napi, work_done);

		rtl_irq_enable(tp, enable_mask);
		mmiowb();
	}

	return work_done;
}


The code needs to check return value of napi_complete_done.

	if (work_done < budget &&
	    napi_complete_done(napi, work_done) {
		rtl_irq_enable(tp, enable_mask);
		mmiowb();
	}

	return work_done;
}

Try that, it might fix the problem and your logic would
be unnecessary