* [PATCH net-next 2/3] mlx4_en: moderate frequency of TX completions
@ 2012-02-23 13:34 Yevgeny Petrilin
2012-02-23 19:44 ` David Miller
0 siblings, 1 reply; 6+ messages in thread
From: Yevgeny Petrilin @ 2012-02-23 13:34 UTC (permalink / raw)
To: davem; +Cc: netdev, yevgenyp
No need to ask for completion for every packet being sent.
So the method is to ask for a completion every 16 packets,
or when the queue is about to be full.
Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
---
drivers/net/ethernet/mellanox/mlx4/en_tx.c | 7 +++++--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index ff32505..e452bba 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -615,6 +615,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
int lso_header_size;
void *fragptr;
bool bounce = false;
+ int ring_busy;
if (!priv->port_up)
goto tx_drop;
@@ -638,8 +639,8 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
vlan_tag = vlan_tx_tag_get(skb);
/* Check available TXBBs And 2K spare for prefetch */
- if (unlikely(((int)(ring->prod - ring->cons)) >
- ring->size - HEADROOM - MAX_DESC_TXBBS)) {
+ ring_busy = (int)(ring->prod - ring->cons) - (ring->size - HEADROOM - MAX_DESC_TXBBS);
+ if (unlikely(ring_busy > 0)) {
/* every full Tx ring stops queue */
netif_tx_stop_queue(netdev_get_tx_queue(dev, tx_ind));
ring->blocked = 1;
@@ -680,6 +681,8 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
!!vlan_tx_tag_present(skb);
tx_desc->ctrl.fence_size = (real_size / 16) & 0x3f;
tx_desc->ctrl.srcrb_flags = priv->ctrl_flags;
+ if (!(!(index & 0xf) || vlan_tag || (ring_busy > -MAX_DESC_TXBBS)))
+ tx_desc->ctrl.srcrb_flags &= cpu_to_be32(~MLX4_WQE_CTRL_CQ_UPDATE);
if (likely(skb->ip_summed == CHECKSUM_PARTIAL)) {
tx_desc->ctrl.srcrb_flags |= cpu_to_be32(MLX4_WQE_CTRL_IP_CSUM |
MLX4_WQE_CTRL_TCP_UDP_CSUM);
--
1.5.4.3
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH net-next 2/3] mlx4_en: moderate frequency of TX completions
2012-02-23 13:34 [PATCH net-next 2/3] mlx4_en: moderate frequency of TX completions Yevgeny Petrilin
@ 2012-02-23 19:44 ` David Miller
2012-02-23 21:13 ` Ben Hutchings
0 siblings, 1 reply; 6+ messages in thread
From: David Miller @ 2012-02-23 19:44 UTC (permalink / raw)
To: yevgenyp; +Cc: netdev
From: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Date: Thu, 23 Feb 2012 15:34:27 +0200
> No need to ask for completion for every packet being sent.
> So the method is to ask for a completion every 16 packets,
> or when the queue is about to be full.
>
> Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
You absolutely cannot do this, you must signal completion and free up
TX queue packets in a finite amount of time.
This means that if you suddenly stop getting new packets to send
you must still free up all the pending TX SKBs even if no more
packets are given to the driver.
Does your hardware unconditionally give a TX completion interrupt when
the TX queue empties completely? If not, then you cannot make the
change contained in this patch.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH net-next 2/3] mlx4_en: moderate frequency of TX completions
2012-02-23 19:44 ` David Miller
@ 2012-02-23 21:13 ` Ben Hutchings
2012-02-23 21:26 ` Ben Hutchings
2012-02-23 21:46 ` David Miller
0 siblings, 2 replies; 6+ messages in thread
From: Ben Hutchings @ 2012-02-23 21:13 UTC (permalink / raw)
To: David Miller; +Cc: yevgenyp, netdev
On Thu, 2012-02-23 at 14:44 -0500, David Miller wrote:
> From: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
> Date: Thu, 23 Feb 2012 15:34:27 +0200
>
> > No need to ask for completion for every packet being sent.
> > So the method is to ask for a completion every 16 packets,
> > or when the queue is about to be full.
> >
> > Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
>
> You absolutely cannot do this, you must signal completion and free up
> TX queue packets in a finite amount of time.
Really, sfc has been doing this forever.
Ben.
> This means that if you suddenly stop getting new packets to send
> you must still free up all the pending TX SKBs even if no more
> packets are given to the driver.
>
> Does your hardware unconditionally give a TX completion interrupt when
> the TX queue empties completely? If not, then you cannot make the
> change contained in this patch.
> --
> To unsubscribe from this list: send the line "unsubscribe netdev" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH net-next 2/3] mlx4_en: moderate frequency of TX completions
2012-02-23 21:13 ` Ben Hutchings
@ 2012-02-23 21:26 ` Ben Hutchings
2012-02-23 21:47 ` David Miller
2012-02-23 21:46 ` David Miller
1 sibling, 1 reply; 6+ messages in thread
From: Ben Hutchings @ 2012-02-23 21:26 UTC (permalink / raw)
To: David Miller; +Cc: yevgenyp, netdev
On Thu, 2012-02-23 at 21:13 +0000, Ben Hutchings wrote:
> On Thu, 2012-02-23 at 14:44 -0500, David Miller wrote:
> > From: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
> > Date: Thu, 23 Feb 2012 15:34:27 +0200
> >
> > > No need to ask for completion for every packet being sent.
> > > So the method is to ask for a completion every 16 packets,
> > > or when the queue is about to be full.
> > >
> > > Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
> >
> > You absolutely cannot do this, you must signal completion and free up
> > TX queue packets in a finite amount of time.
>
> Really, sfc has been doing this forever.
>
> Ben.
>
> > This means that if you suddenly stop getting new packets to send
> > you must still free up all the pending TX SKBs even if no more
> > packets are given to the driver.
> >
> > Does your hardware unconditionally give a TX completion interrupt when
> > the TX queue empties completely? If not, then you cannot make the
> > change contained in this patch.
And it's pretty obvious the hardware has to also send a completion when
the queue is empty. I hope.
Ben.
--
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH net-next 2/3] mlx4_en: moderate frequency of TX completions
2012-02-23 21:13 ` Ben Hutchings
2012-02-23 21:26 ` Ben Hutchings
@ 2012-02-23 21:46 ` David Miller
1 sibling, 0 replies; 6+ messages in thread
From: David Miller @ 2012-02-23 21:46 UTC (permalink / raw)
To: bhutchings; +Cc: yevgenyp, netdev
From: Ben Hutchings <bhutchings@solarflare.com>
Date: Thu, 23 Feb 2012 21:13:56 +0000
> On Thu, 2012-02-23 at 14:44 -0500, David Miller wrote:
>> From: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
>> Date: Thu, 23 Feb 2012 15:34:27 +0200
>>
>> > No need to ask for completion for every packet being sent.
>> > So the method is to ask for a completion every 16 packets,
>> > or when the queue is about to be full.
>> >
>> > Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
>>
>> You absolutely cannot do this, you must signal completion and free up
>> TX queue packets in a finite amount of time.
>
> Really, sfc has been doing this forever.
You have to stop, because otherwise sockets can hang since those
packets can hold a reference to the socket so they must be
released in a finite amount of time regardless of network
traffic.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH net-next 2/3] mlx4_en: moderate frequency of TX completions
2012-02-23 21:26 ` Ben Hutchings
@ 2012-02-23 21:47 ` David Miller
0 siblings, 0 replies; 6+ messages in thread
From: David Miller @ 2012-02-23 21:47 UTC (permalink / raw)
To: bhutchings; +Cc: yevgenyp, netdev
From: Ben Hutchings <bhutchings@solarflare.com>
Date: Thu, 23 Feb 2012 21:26:20 +0000
> And it's pretty obvious the hardware has to also send a completion when
> the queue is empty. I hope.
Right and we know of several chips that don't.
^ permalink raw reply [flat|nested] 6+ messages in thread
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2012-02-23 13:34 [PATCH net-next 2/3] mlx4_en: moderate frequency of TX completions Yevgeny Petrilin
2012-02-23 19:44 ` David Miller
2012-02-23 21:13 ` Ben Hutchings
2012-02-23 21:26 ` Ben Hutchings
2012-02-23 21:47 ` David Miller
2012-02-23 21:46 ` David Miller
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