Re: skb data uncacheable ?? (fwd)

From: Nagendra Singh Tomar
Date: Wed Apr 14 2004 - 07:21:51 EST


On Wed, 14 Apr 2004, Henrik Nordstrom wrote:

> On Wed, 14 Apr 2004, Nagendra Singh Tomar wrote:
>
> > This way we can set the P1 (page containing the header) as cacheable and
> > P2 as noncacheable. I know it looks ugly but we can make use of the
> > remaining of P1 for some slab.
>
> Very doubtful about this. You will need very many of these kinds of pages,
> and I see it very unlikely the relative huge amounts of leftovers will
> find any valuable use elsewhere in the kernel. Basically you increase the
> memory usage per skb from about the packet size plus skbuff header to at
> minimum 2 pages (1 cacheable, one normal), and I do not think many will
> find this acceptable, But maybe?
>
> You also need to worry about tlb flushing and other negative impacts each
> time a new skbuff needs to be allocated / freed.

To avoid this TLB flushing my idea is to have a pre-initialized pool of
such cacheable+noncacheable pages and then allocate from that pool
instead of changing the page attributes, everytime we allocate an SKB.


>
> Regards
> Henrik
>


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