netdev - Re: Difficulties to get 1Gbps on be2net ethernet card

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Date:	Wed, 06 Jun 2012 13:01:24 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jean-Michel Hautbois <jhautbois@...il.com>
Cc:	Sathya.Perla@...lex.com, netdev@...r.kernel.org
Subject: Re: Difficulties to get 1Gbps on be2net ethernet card

On Wed, 2012-06-06 at 12:04 +0200, Jean-Michel Hautbois wrote:

> Well, well, well, after having tested several configurations, several
> drivers, I have a big difference between an old 2.6.26 kernel and a
> newer one (I tried 3.2 and 3.4).
> 
> Here is my stream : UDP packets (multicast), 4000 bytes length, MTU
> set to 4096. I am sending packets only, nothing on RX.
> I send from 1Gbps upto 2.4Gbps and I see no drops in tc with 2.6.26
> kernel, but a lot of drops with a newer kernel.
> So, I don't know if I missed something in my kernel configuration, but
> I have used the 2.6.26 one as a reference, in order to set the same
> options (DMA related, etc).
> 
> I easily reproduce this problem and setting a bigger txqueuelen solves
> it partially.
> 1Gbps requires a txqueulen of 9000, 2.4Gbps requires more than 20000 !
> 
> If you have any idea, I am interested, as this is a big issue for my use case.
> 

Yep.

This driver wants to limit number of tx completions, thats just wrong.

Fix and dirty patch:


diff --git a/drivers/net/ethernet/emulex/benet/be.h b/drivers/net/ethernet/emulex/benet/be.h
index c5c4c0e..1e8f8a6 100644
--- a/drivers/net/ethernet/emulex/benet/be.h
+++ b/drivers/net/ethernet/emulex/benet/be.h
@@ -105,7 +105,7 @@ static inline char *nic_name(struct pci_dev *pdev)
 #define MAX_TX_QS		8
 #define MAX_ROCE_EQS		5
 #define MAX_MSIX_VECTORS	(MAX_RSS_QS + MAX_ROCE_EQS) /* RSS qs + RoCE */
-#define BE_TX_BUDGET		256
+#define BE_TX_BUDGET		65535
 #define BE_NAPI_WEIGHT		64
 #define MAX_RX_POST		BE_NAPI_WEIGHT /* Frags posted at a time */
 #define RX_FRAGS_REFILL_WM	(RX_Q_LEN - MAX_RX_POST)


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