linux-kernel - Re: problems with e1000 and jumboframes

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Message-ID: <20060804061513.GB413@2ka.mipt.ru>
Date:	Fri, 4 Aug 2006 10:15:13 +0400
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	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 Fri, Aug 04, 2006 at 03:59:37PM +1000, Herbert Xu (herbert@...dor.apana.org.au) wrote:
> Chris Leech <chris.leech@...il.com> wrote:
> > 
> > We could try and only use page allocations for older e1000 devices,
> > putting headers and payload into skb->frags and copying the headers
> > out into the skb->data area as needed for processing.  That would do
> > away with large allocations, but in Jesse's experiments calling
> > alloc_page() is slower than kmalloc(), so there can actually be a
> > performance hit from trying to use page allocations all the time.
> 
> Interesting.  Could you guys post figures on alloc_page speed vs. kmalloc?

They probalby measured kmalloc cache access, which only falls to
alloc_pages when cache is refilled, so it will be faster for some short
period of time, but in general (especially for such big-sized
allocations) it is essencially the same.

> Also, getting memory slower is better than not getting them at all :)

Sure.

> -- 
> 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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