Re: [RFC v3 1/3] iwlwifi: mvm: add real TSO implementation

On Thu, 2015-08-20 at 11:15 +0300, Emmanuel Grumbach wrote:

The segmentation is done completely in software. The
driver creates several MPDUs out of a single large send.
Each MPDU is a newly allocated SKB.
A page is allocated to create the headers that need to be
duplicated (SNAP / IP / TCP). The WiFi header is in the
header of the newly created SKBs.

type=feature

Change-Id: I238ffa79cacc5bbdacdfbf3e9673c8d4f02b462a
Signed-off-by: Emmanuel Grumbach <redacted>
---
 drivers/net/wireless/iwlwifi/mvm/tx.c | 513 +++++++++++++++++++++++++++++++---
 1 file changed, 481 insertions(+), 32 deletions(-)

Ouch again.

This will be a NACK. Sorry.


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On 08/20/2015 04:13 PM, Eric Dumazet wrote:

On Thu, 2015-08-20 at 11:15 +0300, Emmanuel Grumbach wrote:

quoted

The segmentation is done completely in software. The
driver creates several MPDUs out of a single large send.
Each MPDU is a newly allocated SKB.
A page is allocated to create the headers that need to be
duplicated (SNAP / IP / TCP). The WiFi header is in the
header of the newly created SKBs.

type=feature

Change-Id: I238ffa79cacc5bbdacdfbf3e9673c8d4f02b462a
Signed-off-by: Emmanuel Grumbach <redacted>
---
 drivers/net/wireless/iwlwifi/mvm/tx.c | 513 +++++++++++++++++++++++++++++++---
 1 file changed, 481 insertions(+), 32 deletions(-)

Ouch again.

This will be a NACK. Sorry.

To be honest, I don't see why. No matter how you look at it, you need to
add headers. And these headers need to sit on some memory that is not
yet allocated. skb_gso_segment allocates new skb which is a memory
allocation.

I looked at ethernet/marvell/mvneta.c (which uses net/core/tso.c) and
they pre-allocate DMA coherent memory for the additional headers they
create. I can have pre-allocated pages if you want.