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Date:      Wed, 27 Feb 2002 10:58:13 -0800 (PST)
From:      Julian Elischer <julian@elischer.org>
To:        Bosko Milekic <bmilekic@unixdaemons.com>
Cc:        Jeff Roberson <jroberson@chesapeake.net>, arch@FreeBSD.ORG
Subject:   Re: mbuf allocation. (was: Slab allocator)
Message-ID:  <Pine.BSF.4.21.0202271051280.97278-100000@InterJet.elischer.org>
In-Reply-To: <20020227124945.A29065@unixdaemons.com>

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On Wed, 27 Feb 2002, Bosko Milekic wrote:

> 
>   (iii) For what concerns mbuf allocations, I don't know what to tell
>         you right now. Ultimately, I would like to see uma eventually
> 	replace mb_alloc. However, I would like to make sure that the
> 	transition is smooth and painless and that we don't lose any
> 	performance. This is why I think that co-existing uma with all
> 	existing code (see (ii)) is a good idea. Then, if you're
> 	willing, I would be glad to help "attach" mbuf allocations to
> 	uma, should that be possible and should we decide, as a group,
> 	that that is what we want to do.

On the topic of mbuf allocation:
if we have a slab allocator it wouldn't matter if we have a 
3rd size of mbuf, just the size of a mbuf header structure (with packet
header) that gets used whenever a cluster-mbuf combo is allocated.
This fits in with the comment that someone made recently about having an
allocator function for a mbuf+cluster instead of having
the caller allolcate one and hte add a cluster to it.

I know of no code that takes an mbuf cluster,
strips off the cluster, and then uses it as a normal mbuf, so the extra
200 bytes being carried around is always wasted.


 


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