Re: skb data uncacheable ??

From: Henrik Nordstrom
Date: Wed Apr 14 2004 - 02:16:19 EST


On Wed, 14 Apr 2004, Nagendra Singh Tomar wrote:

> > This should not be difficult if using non-linear sk_buff.
>
> You are right, but when I was writing this mail I had non-SG devices in
> mind. Even for a regular ethernet frame of 1500 bytes we can gain a lot
> if can put the data portion in noncacheable region.

If you want different cache status for header and rest of data you need to
split the allocations to different zones. To be able to have the
allocation split the sk_buff must be non-linear. This from the requirement
of different cache levels and is independent of the type of driver/device
used.

Yes, this means each and every driver needs to be modified to use the
feature, but so is often the case when adding new features.

> > I am doubtful, but I am possibly biased from working a lot with iptables
> > and often accessing the payload while the packet is forwarded for NAT
> > etc.. but maybe.
>
> If the data payload has to be touched in anyway then putting it in
> noncacheable area will turn to be a killer.

Which is why I say I am possibly biased.. not everyone needs to access the
data payload beyond the headers.

Regards
Henrik

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