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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Robert Hancock <robert.hancock@calian.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 5.15 799/846] net: axienet: increase default TX ring size to 128
Date:   Mon, 24 Jan 2022 19:45:16 +0100
Message-Id: <20220124184128.507976561@linuxfoundation.org>
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From: Robert Hancock <robert.hancock@calian.com>

commit 2d19c3fd80178160dd505ccd7fed1643831227a5 upstream.

With previous changes to make the driver handle the TX ring size more
correctly, the default TX ring size of 64 appears to significantly
bottleneck TX performance to around 600 Mbps on a 1 Gbps link on ZynqMP.
Increasing this to 128 seems to bring performance up to near line rate and
shouldn't cause excess bufferbloat (this driver doesn't yet support modern
byte-based queue management).

Fixes: 8a3b7a252dca9 ("drivers/net/ethernet/xilinx: added Xilinx AXI Ethernet driver")
Signed-off-by: Robert Hancock <robert.hancock@calian.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/xilinx/xilinx_axienet_main.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
@@ -41,7 +41,7 @@
 #include "xilinx_axienet.h"
 
 /* Descriptors defines for Tx and Rx DMA */
-#define TX_BD_NUM_DEFAULT		64
+#define TX_BD_NUM_DEFAULT		128
 #define RX_BD_NUM_DEFAULT		1024
 #define TX_BD_NUM_MIN			(MAX_SKB_FRAGS + 1)
 #define TX_BD_NUM_MAX			4096