linux-kernel - Re: [PATCH v2] xen-netfront: Fix Rx stall during network stress and OOM

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Date:   Fri, 20 Jan 2017 14:09:13 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     vineethp@...zon.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] xen-netfront: Fix Rx stall during network stress
 and OOM

From: Vineeth Remanan Pillai <vineethp@...zon.com>
Date: Thu, 19 Jan 2017 08:35:39 -0800

> From: Vineeth Remanan Pillai <vineethp@...zon.com>
> 
> During an OOM scenario, request slots could not be created as skb
> allocation fails. So the netback cannot pass in packets and netfront
> wrongly assumes that there is no more work to be done and it disables
> polling. This causes Rx to stall.
> 
> The issue is with the retry logic which schedules the timer if the
> created slots are less than NET_RX_SLOTS_MIN. The count of new request
> slots to be pushed are calculated as a difference between new req_prod
> and rsp_cons which could be more than the actual slots, if there are
> unconsumed responses.
> 
> The fix is to calculate the count of newly created slots as the
> difference between new req_prod and old req_prod.
> 
> Signed-off-by: Vineeth Remanan Pillai <vineethp@...zon.com>
> Reviewed-by: Juergen Gross <jgross@...e.com>
> ---
> Changes in v2:
> 	- Removed the old implementation of enabling polling on
> 	  skb allocation error.
> 	- Corrected the refill timer logic to schedule when newly
> 	  created slots since last push is less than NET_RX_SLOTS_MIN.

Applied.