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Subject: Re: [PATCH v2] xen-netfront: Fix Rx stall during network stress and
 OOM
To: Remanan Pillai <vineethp@u480fcf3b67f557f68df1.ant.amazon.com>,
        boris.ostrovsky@oracle.com, xen-devel@lists.xenproject.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
References: <0cb06b48-cb3c-47aa-2ae6-3a70197a5b64@amazon.com>
 <1484330100-3960-1-git-send-email-vineethp@u480fcf3b67f557f68df1.ant.amazon.com>
Cc: Vineeth Remanan Pillai <vineethp@amazon.com>, kamatam@amazon.com,
        aliguori@amazon.com
From: Juergen Gross <jgross@suse.com>
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Date: Mon, 16 Jan 2017 07:24:05 +0100
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On 13/01/17 18:55, Remanan Pillai wrote:
> From: Vineeth Remanan Pillai <vineethp@amazon.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@amazon.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Thanks,

Juergen