Home » Mailing list archives » linux-netdev » 2009 » March » 25

[PATCH] ucc_geth: Move freeing of TX packets to NAPI context.

Previous thread: Short Notice (Winners Alert!!!) by Global Promo on Wednesday, March 25, 2009 - 6:21 am. (1 message)

Next thread: [PATCH] Re: Next March 25: net/netfilter/xt_LED build failure. by Subrata Modak on Wednesday, March 25, 2009 - 6:57 am. (2 messages)
[view original message]
From: Joakim Tjernlund
Subject: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Wednesday, March 25, 2009 - 6:30 am

>From 1c2f23b1f37f4818c0fd0217b93eb38ab6564840 Mon Sep 17 00:00:00 2001
From: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Date: Tue, 24 Mar 2009 10:19:27 +0100
Subject: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
 Also increase NAPI weight somewhat.
 This will make the system alot more responsive while
 ping flooding the ucc_geth ethernet interaface.


Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
---
 drivers/net/ucc_geth.c |   30 +++++++++++-------------------
 drivers/net/ucc_geth.h |    2 +-
 2 files changed, 12 insertions(+), 20 deletions(-)

diff --git a/drivers/net/ucc_geth.c b/drivers/net/ucc_geth.c
index 097aed8..7d5d110 100644
--- a/drivers/net/ucc_geth.c
+++ b/drivers/net/ucc_geth.c
@@ -3214,7 +3214,7 @@ static int ucc_geth_tx(struct net_device *dev, u8 txQ)
 		dev->stats.tx_packets++;
 
 		/* Free the sk buffer associated with this TxBD */
-		dev_kfree_skb_irq(ugeth->
+		dev_kfree_skb(ugeth->
 				  tx_skbuff[txQ][ugeth->skb_dirtytx[txQ]]);
 		ugeth->tx_skbuff[txQ][ugeth->skb_dirtytx[txQ]] = NULL;
 		ugeth->skb_dirtytx[txQ] =
@@ -3248,9 +3248,16 @@ static int ucc_geth_poll(struct napi_struct *napi, int budget)
 	for (i = 0; i < ug_info->numQueuesRx; i++)
 		howmany += ucc_geth_rx(ugeth, i, budget - howmany);
 
+	/* Tx event processing */
+	spin_lock(&ugeth->lock);
+	for (i = 0; i < ug_info->numQueuesTx; i++) {
+		ucc_geth_tx(ugeth->dev, i);
+	}
+	spin_unlock(&ugeth->lock);
+
 	if (howmany < budget) {
 		netif_rx_complete(napi);
-		setbits32(ugeth->uccf->p_uccm, UCCE_RX_EVENTS);
+		setbits32(ugeth->uccf->p_uccm, UCCE_RX_EVENTS | UCCE_TX_EVENTS);
 	}
 
 	return howmany;
@@ -3264,8 +3271,6 @@ static irqreturn_t ucc_geth_irq_handler(int irq, void *info)
 	struct ucc_geth_info *ug_info;
 	register u32 ucce;
 	register u32 uccm;
-	register u32 tx_mask;
-	u8 i;
 
 	ugeth_vdbg("%s: IN", __func__);
 
@@ -3279,27 +3284,14 @@ static irqreturn_t ucc_geth_irq_handler(int irq, void *info)
 	out_be32(uccf->p_ucce, ...
[ message continues ]
[view original message]
From: Eric Dumazet
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Wednesday, March 25, 2009 - 7:04 am

Cant you test (ucce & UCCE_TX_EVENTS) or something here to avoid

Why tx completions dont change "howmany" ?


--


[ message continues ]
[view original message]
From: Joakim Tjernlund
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Wednesday, March 25, 2009 - 8:16 am

Probably, but I want this patch as simple as possible. There
account tx event above...

This is unclear and last I checked not very common amongst other drivers 
in the
tree.

UCC_GETH_DEV_WEIGHT needs to be a bit bigger than the number of RX HW 
buffers avaliable,
otherwise one won't be able to drain the whole queue in one go. Changing
weight to something bigger made a big difference.

 Jocke
--


[ message continues ]
[view original message]
From: David Miller
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Wednesday, March 25, 2009 - 2:42 pm

From: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>

You're not supposed to "drain the whole queue in one go", that
is not the goal of the weight value.

The goal of the weight value is that it is low enough such that
other devices also scheduled for NAPI on the current processor
can get some fair time to process packets too.
--


[ message continues ]
[view original message]
From: David Miller
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Wednesday, March 25, 2009 - 2:40 pm

From: Eric Dumazet <dada1@cosmosbay.com>

He should leave howmany alone for TX work and use a weight
value of 64 just like most other drivers in the tree do.

Due to the abuse and random ignorant fiddling of the
weight value, I am going to make it something the core
rather than drivers choose.
--


[ message continues ]
[view original message]
From: Joakim Tjernlund
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Wednesday, March 25, 2009 - 2:55 pm

Good, I had a hard time finding info how one should use it anyway. 

--


[ message continues ]
[view original message]
From: Anton Vorontsov
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Wednesday, March 25, 2009 - 7:25 am

Some time ago I've tried a similar thing for this driver, but during
tcp (or udp I don't quite remember) netperf tests I was getting tx
watchdog timeouts after ~2-5 minutes of work. I was testing with a
gigabit and 100 Mbit link, with 100 Mbit link the issue was not
reproducible.

Though, I recalling I was doing a bit more than your patch: I was
also clearing the TX events in the ucce register before calling
ucc_geth_tx, that way I was trying to avoid stale interrupts. That
helped to increase an overall performance (not only responsiveness),
but as I said my approach didn't pass the tests.

I don't really think that your patch may cause this, but can you
try netperf w/ this patch applied anyway? And see if it really
doesn't cause any issues under stress?

Thanks,

-- 
Anton Vorontsov
email: cbouatmailru@gmail.com
irc://irc.freenode.net/bd2
--


[ message continues ]
[view original message]
From: Joakim Tjernlund
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Wednesday, March 25, 2009 - 8:21 am

Ran this on my host against my target board:
 netperf -t UDP_RR  -H 192.168.1.16
 netperf -t UDP_STREAM -H 192.168.1.16
 netperf -t TCP_STREAM -H 192.168.1.16
 netperf -t TCP_SENDFILE -H 192.168.1.16
 netperf -t TCP_MAERTS -H 192.168.1.16
 netperf -t TCP_RR -H 192.168.1.16
 netperf -t TCP_CRR -H 192.168.1.16

Didn't notice any timeouts, but I only have 100Mbit interfaces.
--


[ message continues ]
[view original message]
From: Joakim Tjernlund
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Wednesday, March 25, 2009 - 10:51 am

Does the line(in ucc_geth_tx()) look OK to you:
        if ((bd == ugeth->txBd[txQ]) && (netif_queue_stopped(dev) == 0))
                        break;

Sure does look fishy to me.
--


[ message continues ]
[view original message]
From: Li Yang
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Monday, March 30, 2009 - 1:34 am

On Thu, Mar 26, 2009 at 1:51 AM, Joakim Tjernlund

There are two cases when txBd=ConfBd: the BD ring is full or empty.
The condition used here ensures that it is the empty case.  Because in
hard_start_xmit, the queue will be stopped when the BD ring is full.
Maybe some comment is needed here.

- Leo
--


[ message continues ]
[view original message]
From: Joakim Tjernlund
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Monday, March 30, 2009 - 2:21 am

But how do you know that the queue hasn't been stopped by someone else 
than
the driver? 
If it is stopped by higher layers, the if stmt will fail.

 Jocke
--


[ message continues ]
[view original message]
From: Li Yang
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Monday, March 30, 2009 - 2:36 am

On Mon, Mar 30, 2009 at 5:21 PM, Joakim Tjernlund

It looks like from existing code that only the driver can legally stop
the queue.  I'm not 100% sure though.  Correct me if I'm wrong.

- Leo
--


[ message continues ]
[view original message]
From: Joakim Tjernlund
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Monday, March 30, 2009 - 3:01 am

I don't know. But the question you should ask is: Does the networking
code promise this now and for the future? If not, you should
fix the driver not to relay on netif_queue_stopped() here.

 Jocke
--


[ message continues ]
[view original message]
From: Li Yang
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Monday, March 30, 2009 - 3:24 am

On Mon, Mar 30, 2009 at 6:01 PM, Joakim Tjernlund

Right.  But it's beyond my knowledge to answer this question.  If not,
adding a device specific flag is not very costing.

Hi Dave,

Can we assume that the netif_stop_queue() and netif_wake_queue() are
only used by the netdev driver?  And the queue state will not be
changed by other part of the networking subsystem?

- Leo
--


[ message continues ]
[view original message]
From: David Miller
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Monday, March 30, 2009 - 1:36 pm

From: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>

Stop this nonsense talk.

If the driver can't be the one and only controller of the TX queue
state, everything would essentially explode.

The fact is, it does.
--


[ message continues ]
[view original message]
From: David Miller
Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
Date: Wednesday, March 25, 2009 - 2:39 pm

From: Joakim Tjernlund <joakim.tjernlund@transmode.se>

The weight is not for the sake of your device, it's for
the sake of fairness with others.

Please just use 64, like every other driver does.

I'm not applying this.
--


[ message continues ]
Previous thread: Short Notice (Winners Alert!!!) by Global Promo on Wednesday, March 25, 2009 - 6:21 am. (1 message)

Next thread: [PATCH] Re: Next March 25: net/netfilter/xt_LED build failure. by Subrata Modak on Wednesday, March 25, 2009 - 6:57 am. (2 messages)