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Date: Wed, 2 Jun 2004 07:12:34 -0700
From: Bosko Milekic <bmilekic@FreeBSD.org>
To: Gleb Smirnoff <glebius@cell.sick.ru>
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Subject: Re: [HEADS-UP] mbuma is in the tree
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>  Bosko,

[deletia]

>  are you going to convert mbuf tag allocator to UMA? Now
>tags are allocated with malloc(). AFAIK, tags are used heavily in pf,
>and forthcoming ALTQ. Moving to UMA should affect their performance
>positively.

  First off, malloc() *is* UMA.  With mbuma in the tree, I don't believe
  we have any remaining custom-allocators in the tree.

  As for what to do with m_tags, it is still unclear to me.  Personally,
  I'm conflicted about their use.  On one hand, they offer a clean way
  to attach metadata to packets, but on the other hand they are quite
  expensive.

  If you read the paper on mbuma, you'll notice that I point out that it
  would be worth investigating whether, in scenarios where an m_tag is
  ALWAYS required per packet (e.g., MAC), providing a secondary zone with
  pre-allocated m_tags for packet headers might be worth it.  Prior to
  this work, however, I suggest we investigate the possibility of using
  smaller mini-mbufs whenever clusters are used so that space wastage
  is reduced.

  -Bosko