* [PATCH net-next-2.6] e1000: save skb counts in TX to avoid cache misses
@ 2011-08-26 0:39 Dean Nelson
2011-08-26 3:52 ` Jeff Kirsher
0 siblings, 1 reply; 3+ messages in thread
From: Dean Nelson @ 2011-08-26 0:39 UTC (permalink / raw)
To: netdev, Jeff Kirshier; +Cc: Andy Gospodarek
Virtual Machines with emulated e1000 network adapter running on Parallels'
server were seeing kernel panics due to the e1000 driver dereferencing an
unexpected NULL pointer retrieved from buffer_info->skb.
The problem has been addressed for the e1000e driver, but not for the e1000.
Since the two drivers share similar code in the affected area, a port of the
following e1000e driver commit solves the issue for the e1000 driver:
commit 9ed318d546a29d7a591dbe648fd1a2efe3be1180
Author: Tom Herbert <therbert@google.com>
Date: Wed May 5 14:02:27 2010 +0000
e1000e: save skb counts in TX to avoid cache misses
In e1000_tx_map, precompute number of segements and bytecounts which
are derived from fields in skb; these are stored in buffer_info. When
cleaning tx in e1000_clean_tx_irq use the values in the associated
buffer_info for statistics counting, this eliminates cache misses
on skb fields.
Signed-off-by: Dean Nelson <dnelson@redhat.com>
---
This patch (backported to RHEL6.2) was verified by Dmitry Skorodumov to solve
Parallels' reported problem.
drivers/net/ethernet/intel/e1000/e1000.h | 2 ++
drivers/net/ethernet/intel/e1000/e1000_main.c | 18 +++++++++---------
2 files changed, 11 insertions(+), 9 deletions(-)
diff --git a/drivers/net/ethernet/intel/e1000/e1000.h b/drivers/net/ethernet/intel/e1000/e1000.h
index 24f41da..4ea87b1 100644
--- a/drivers/net/ethernet/intel/e1000/e1000.h
+++ b/drivers/net/ethernet/intel/e1000/e1000.h
@@ -150,6 +150,8 @@ struct e1000_buffer {
unsigned long time_stamp;
u16 length;
u16 next_to_watch;
+ unsigned int segs;
+ unsigned int bytecount;
u16 mapped_as_page;
};
diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c
index 7c280e5..4a32c15 100644
--- a/drivers/net/ethernet/intel/e1000/e1000_main.c
+++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
@@ -2848,7 +2848,7 @@ static int e1000_tx_map(struct e1000_adapter *adapter,
struct e1000_buffer *buffer_info;
unsigned int len = skb_headlen(skb);
unsigned int offset = 0, size, count = 0, i;
- unsigned int f;
+ unsigned int f, bytecount, segs;
i = tx_ring->next_to_use;
@@ -2949,7 +2949,13 @@ static int e1000_tx_map(struct e1000_adapter *adapter,
}
}
+ segs = skb_shinfo(skb)->gso_segs ?: 1;
+ /* multiply data chunks by size of headers */
+ bytecount = ((segs - 1) * skb_headlen(skb)) + skb->len;
+
tx_ring->buffer_info[i].skb = skb;
+ tx_ring->buffer_info[i].segs = segs;
+ tx_ring->buffer_info[i].bytecount = bytecount;
tx_ring->buffer_info[first].next_to_watch = i;
return count;
@@ -3623,14 +3629,8 @@ static bool e1000_clean_tx_irq(struct e1000_adapter *adapter,
cleaned = (i == eop);
if (cleaned) {
- struct sk_buff *skb = buffer_info->skb;
- unsigned int segs, bytecount;
- segs = skb_shinfo(skb)->gso_segs ?: 1;
- /* multiply data chunks by size of headers */
- bytecount = ((segs - 1) * skb_headlen(skb)) +
- skb->len;
- total_tx_packets += segs;
- total_tx_bytes += bytecount;
+ total_tx_packets += buffer_info->segs;
+ total_tx_bytes += buffer_info->bytecount;
}
e1000_unmap_and_free_tx_resource(adapter, buffer_info);
tx_desc->upper.data = 0;
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH net-next-2.6] e1000: save skb counts in TX to avoid cache misses
2011-08-26 0:39 [PATCH net-next-2.6] e1000: save skb counts in TX to avoid cache misses Dean Nelson
@ 2011-08-26 3:52 ` Jeff Kirsher
2011-08-26 16:55 ` David Miller
0 siblings, 1 reply; 3+ messages in thread
From: Jeff Kirsher @ 2011-08-26 3:52 UTC (permalink / raw)
To: Dean Nelson; +Cc: netdev, Andy Gospodarek
[-- Attachment #1: Type: text/plain, Size: 1186 bytes --]
On Thu, 2011-08-25 at 17:39 -0700, Dean Nelson wrote:
> Virtual Machines with emulated e1000 network adapter running on
> Parallels'
> server were seeing kernel panics due to the e1000 driver dereferencing
> an
> unexpected NULL pointer retrieved from buffer_info->skb.
>
> The problem has been addressed for the e1000e driver, but not for the
> e1000.
> Since the two drivers share similar code in the affected area, a port
> of the
> following e1000e driver commit solves the issue for the e1000 driver:
>
> commit 9ed318d546a29d7a591dbe648fd1a2efe3be1180
> Author: Tom Herbert <therbert@google.com>
> Date: Wed May 5 14:02:27 2010 +0000
>
> e1000e: save skb counts in TX to avoid cache misses
>
> In e1000_tx_map, precompute number of segements and bytecounts
> which
> are derived from fields in skb; these are stored in buffer_info.
> When
> cleaning tx in e1000_clean_tx_irq use the values in the associated
> buffer_info for statistics counting, this eliminates cache misses
> on skb fields.
>
>
> Signed-off-by: Dean Nelson <dnelson@redhat.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Looks fine.
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH net-next-2.6] e1000: save skb counts in TX to avoid cache misses
2011-08-26 3:52 ` Jeff Kirsher
@ 2011-08-26 16:55 ` David Miller
0 siblings, 0 replies; 3+ messages in thread
From: David Miller @ 2011-08-26 16:55 UTC (permalink / raw)
To: jeffrey.t.kirsher; +Cc: dnelson, netdev, andy
From: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Date: Thu, 25 Aug 2011 20:52:39 -0700
> On Thu, 2011-08-25 at 17:39 -0700, Dean Nelson wrote:
>> Virtual Machines with emulated e1000 network adapter running on
>> Parallels'
>> server were seeing kernel panics due to the e1000 driver dereferencing
>> an
>> unexpected NULL pointer retrieved from buffer_info->skb.
>>
>> The problem has been addressed for the e1000e driver, but not for the
>> e1000.
>> Since the two drivers share similar code in the affected area, a port
>> of the
>> following e1000e driver commit solves the issue for the e1000 driver:
>>
>> commit 9ed318d546a29d7a591dbe648fd1a2efe3be1180
>> Author: Tom Herbert <therbert@google.com>
>> Date: Wed May 5 14:02:27 2010 +0000
>>
>> e1000e: save skb counts in TX to avoid cache misses
>>
>> In e1000_tx_map, precompute number of segements and bytecounts
>> which
>> are derived from fields in skb; these are stored in buffer_info.
>> When
>> cleaning tx in e1000_clean_tx_irq use the values in the associated
>> buffer_info for statistics counting, this eliminates cache misses
>> on skb fields.
>>
>>
>> Signed-off-by: Dean Nelson <dnelson@redhat.com>
>
> Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Applied, thanks.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2011-08-26 0:39 [PATCH net-next-2.6] e1000: save skb counts in TX to avoid cache misses Dean Nelson
2011-08-26 3:52 ` Jeff Kirsher
2011-08-26 16:55 ` David Miller
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