From: Ed Cashin <hidden> Date: 2012-09-19 18:29:24
A change in a series of VLAN-related changes appears to have
inadvertently disabled the use of the scatter gather feature of
network cards for transmission of non-IP ethernet protocols like ATA
over Ethernet (AoE). Below is a reference to the commit that
introduces a "harmonize_features" function that turns off scatter
gather when the NIC does not support hardware checksumming for the
ethernet protocol of an sk buff.
commit f01a5236bd4b140198fbcc550f085e8361fd73fa
Author: Jesse Gross [off-list ref]
Date: Sun Jan 9 06:23:31 2011 +0000
net offloading: Generalize netif_get_vlan_features().
The can_checksum_protocol function is not equipped to consider a
protocol that does not require checksumming. Calling it for a
protocol that requires no checksum is inappropriate.
The patch below has harmonize_features call can_checksum_protocol when
the protocol needs a checksum, so that the network layer is not forced
to perform unnecessary skb linearization on the transmission of AoE
packets. Unnecessary linearization results in decreased performance
and increased memory pressure, as reported here:
http://www.spinics.net/lists/linux-mm/msg15184.html
The problem has probably not been widely experienced yet, because
only recently has the kernel.org-distributed aoe driver acquired the
ability to use payloads of over a page in size, with the patchset
recently included in the mm tree:
https://lkml.org/lkml/2012/8/28/140
The coraid.com-distributed aoe driver already could use payloads of
greater than a page in size, but its users generally do not use the
newest kernels.
Signed-off-by: Ed Cashin <redacted>
---
net/core/dev.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
From: Ben Hutchings <hidden> Date: 2012-09-19 19:55:09
On Tue, 2012-09-18 at 20:20 -0400, Ed Cashin wrote:
A change in a series of VLAN-related changes appears to have
inadvertently disabled the use of the scatter gather feature of
network cards for transmission of non-IP ethernet protocols like ATA
over Ethernet (AoE). Below is a reference to the commit that
introduces a "harmonize_features" function that turns off scatter
gather when the NIC does not support hardware checksumming for the
ethernet protocol of an sk buff.
commit f01a5236bd4b140198fbcc550f085e8361fd73fa
Author: Jesse Gross [off-list ref]
Date: Sun Jan 9 06:23:31 2011 +0000
net offloading: Generalize netif_get_vlan_features().
The can_checksum_protocol function is not equipped to consider a
protocol that does not require checksumming. Calling it for a
protocol that requires no checksum is inappropriate.
the generic way to check that would be skb->ip_summed != CHECKSUM_NONE.
Ben.
+ !can_checksum_protocol(features, protocol)) {
features &= ~NETIF_F_ALL_CSUM;
features &= ~NETIF_F_SG;
} else if (illegal_highdma(skb->dev, skb)) {
--
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.
From: David Miller <davem@davemloft.net> Date: 2012-09-19 20:00:13
Date: Tue, 18 Sep 2012 20:20:36 -0400
Please do not incorporate the date of the commit in your local tree
into the Date: field advertised in your outgoing emails when you post
patches.
You did not post this on September 18th, you posted it on September
19th.
When you post patches the way you did, it screws up the ordering
of my patch queue at:
http://patchwork.ozlabs.org/project/netdev/list/
since it is sorted by the Date: in the patch's email.
Therefore if you just use the normal email posting date it makes
my life a lot easier and it makes sure patches will be looked at
and processed in the correct order.
Thanks.
From: Ed Cashin <hidden> Date: 2012-09-20 01:17:06
This two-part patchset replaces an earlier net-only patch that
added an explicit check for the AoE protocol to harmonize_features
in net/core/dev.c.
Following the suggestion of Ben Hutchings, this patchset makes
the decision in the network layer protocol agnostic instead of
using ETH_P_AOE as a special case.
Ed L. Cashin (2):
aoe: mark AoE packets as requiring no checksumming
net: do not disable sg for packets requiring no checksum
drivers/block/aoe/aoecmd.c | 1 +
net/core/dev.c | 3 ++-
2 files changed, 3 insertions(+), 1 deletions(-)
--
1.7.2.5
From: Ed Cashin <hidden> Date: 2012-09-20 01:17:47
In order for the network layer to see that AoE requires
no checksumming in a generic way, packets should be marked
CHECKSUM_NONE.
Rather than relying on the current behavior of alloc_skb,
this change causes the aoe driver to explicitly mark its
packets as requiring no checksum.
Signed-off-by: Ed Cashin <redacted>
---
drivers/block/aoe/aoecmd.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
From: Ed Cashin <hidden> Date: 2012-09-20 01:20:34
A change in a series of VLAN-related changes appears to have
inadvertently disabled the use of the scatter gather feature of
network cards for transmission of non-IP ethernet protocols like ATA
over Ethernet (AoE). Below is a reference to the commit that
introduces a "harmonize_features" function that turns off scatter
gather when the NIC does not support hardware checksumming for the
ethernet protocol of an sk buff.
commit f01a5236bd4b140198fbcc550f085e8361fd73fa
Author: Jesse Gross [off-list ref]
Date: Sun Jan 9 06:23:31 2011 +0000
net offloading: Generalize netif_get_vlan_features().
The can_checksum_protocol function is not equipped to consider a
protocol that does not require checksumming. Calling it for a
protocol that requires no checksum is inappropriate.
The patch below has harmonize_features call can_checksum_protocol when
the protocol needs a checksum, so that the network layer is not forced
to perform unnecessary skb linearization on the transmission of AoE
packets. Unnecessary linearization results in decreased performance
and increased memory pressure, as reported here:
http://www.spinics.net/lists/linux-mm/msg15184.html
The problem has probably not been widely experienced yet, because
only recently has the kernel.org-distributed aoe driver acquired the
ability to use payloads of over a page in size, with the patchset
recently included in the mm tree:
https://lkml.org/lkml/2012/8/28/140
The coraid.com-distributed aoe driver already could use payloads of
greater than a page in size, but its users generally do not use the
newest kernels.
Signed-off-by: Ed Cashin <redacted>
---
net/core/dev.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
From: Ben Hutchings <hidden> Date: 2012-09-20 01:25:10
On Wed, 2012-09-19 at 18:17 -0700, Ed Cashin wrote:
In order for the network layer to see that AoE requires
no checksumming in a generic way, packets should be marked
CHECKSUM_NONE.
Which they are by default.
quoted hunk
Rather than relying on the current behavior of alloc_skb,
this change causes the aoe driver to explicitly mark its
packets as requiring no checksum.
Signed-off-by: Ed Cashin <redacted>
---
drivers/block/aoe/aoecmd.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
Can be written as:
skb_checksum_none_assert(skb);
if you really want to be sure.
Ben.
}
return skb;
}
--
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.