Re: [PATCH v1 6/7] net: mvneta: Don't use GRO on Armada 3720

On Thu, 9 Aug 2018 20:08:32 +0800
Jisheng Zhang [off-list ref] wrote:

On Thu, 9 Aug 2018 19:27:55 +0800 Jisheng Zhang wrote:

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Hi,

On Thu, 9 Aug 2018 12:40:41 +0800 Jisheng Zhang wrote:
  

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+ more people

On Wed,  8 Aug 2018 17:27:05 +0200 Marek Behún wrote:
    

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For some reason on Armada 3720 boards (EspressoBin and Turris
Mox) the networking driver behaves weirdly when using
napi_gro_receive.

For example downloading a big file from a local network (low
ping) is fast, but when downloading from a remote server
(higher ping), the download speed is at first high but drops
rapidly to almost nothing or absolutely nothing.      

We also met this issue on some berlin platforms. I tried to fix
the bug, but no clue so far.
    

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This is fixed when using netif_receive_skb instead of
napi_gro_receive.      

This is a workaround. The good news is this workaround also fixes
the issue we saw on berlin.
    

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Signed-off-by: Marek Behun <redacted>
Cc: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: netdev@vger.kernel.org

diff --git a/drivers/net/ethernet/marvell/mvneta.c

b/drivers/net/ethernet/marvell/mvneta.c index
0ad2f3f7da85..27f3017d94c5 100644 ---
a/drivers/net/ethernet/marvell/mvneta.c +++
b/drivers/net/ethernet/marvell/mvneta.c @@ -1959,7 +1959,10 @@
static int mvneta_rx_swbm(struct mvneta_port *pp, int rx_todo, 
 			skb->protocol = eth_type_trans(skb,
dev); mvneta_rx_csum(pp, rx_status, skb);
-			napi_gro_receive(&port->napi, skb);
+			if (pp->neta_armada3700)
+				netif_receive_skb(skb);
+			else
+				napi_gro_receive(&port->napi,
skb);    

I think I found the root cause, if neta_armada3700 is true, the
port got from this_cpu_ptr(pp->ports) is invalid, this is bug...
I'll cook a patch for this  

correct it as:

the port's(port is got from this_cpu_ptr(pp->ports) napi is invalid.

Patch is sent out. Could you please try?

Per my test, it solves the issue we saw on berlin.

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Thanks
  

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 			rcvd_pkts++;
 			rcvd_bytes += rx_bytes;

@@ -2001,7 +2004,10 @@ static int mvneta_rx_swbm(struct

mvneta_port *pp, int rx_todo, 
 		mvneta_rx_csum(pp, rx_status, skb);
 
-		napi_gro_receive(&port->napi, skb);
+		if (pp->neta_armada3700)
+			netif_receive_skb(skb);
+		else
+			napi_gro_receive(&port->napi, skb);
 	}
 
 	if (rcvd_pkts) {      

Jisheng, the issue is solved with your patch. Thanks :)