linux-kernel - Re: problems with e1000 and jumboframes

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Message-ID: <20060805102435.GA15740@2ka.mipt.ru>
Date:	Sat, 5 Aug 2006 14:24:36 +0400
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Jesse Brandeburg <jesse.brandeburg@...il.com>,
	Chris Leech <chris.leech@...il.com>, arnd@...dnet.de,
	olel@....pl, linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: problems with e1000 and jumboframes

On Sat, Aug 05, 2006 at 08:09:54PM +1000, Herbert Xu (herbert@...dor.apana.org.au) wrote:
> > If you can create several skbs and link them togeter you defenitely can
> > organize pages into frag_list, just get pages from different skb->data
> > and free those skbs.
> 
> Having a more flexible mechanism for managing skb_shared_info->frags
> would definitely be an improvement.  At the moment we can't indicate
> whether the individual frags are writable so we assume every frag to
> be read-only.

Having one page inside frag_list writable does not make a lot of sence,
so we really need either all of them writable, or nothing.
And it is much less error-prone to assume that every page is read-only.

> If we had a flag to indicate writability we could also have a flag to
> indicate that the memory comes from kmalloc rather than alloc_page.

Yes, that would be good, but who will give us a bit in the struct page?
Can we recreate frag_list elements to be a bitmasks and steal couple
of them there, so we would not increase fragment's structure size?

> Cheers,
> -- 
> Visit Openswan at http://www.openswan.org/
> Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

-- 
	Evgeniy Polyakov
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