Jeff Roberson wrote:
http://people.freebsd.org/~jeff/mbuf_ref2.diff
Hello,
I have been experimenting with different revisions to the mbuf api to
improve performance and simplify code. This patch is the first of
several proposed steps towards those goals. The aim of this patch is
two fold;
1) Revising the reference counting system so that we can eliminate
reference uma zones and the significant uma_find_refcnt() costs in some
workloads. This is done by making all mbufs reference counted and using
the owning mbuf's ref for the ext_ref. In this model we never reference
data, we only reference other mbufs owning the data.
2) Improve allocation and free performance by reducing the special
cases in the format and using inlines when appropriate. In particular,
the simplification of the m_ext structure yields less code and confusion
for dealing with external storage on free. The ctor/dtor mbuf routines
are no longer used. A zone pointer and length was added to struct mbuf
to simplify free and size calculations.
A number of routines were made much, much simpler by the addition of a
16bit size field. Previously we dependend on calculating the size by
figuring out if it was an ext, pkthdr, or standard mbuf. Ultimately,
this patch moves us closer to having a size agnostic mbuf which we can
use to experiment with different allocation sizes or even backending to
malloc for dynamically sized mbufs.
I would appreciate testing feedback from varied workloads to make sure
there are no bugs before I go forward with this. I have tested only
host oriented networking with a few drivers. It is not anticipated that
there will be any significant incompatibilities introduced with this
round but there is always that possibility.
generally I like it.
We discussed someof this before..
It would be nice if you added more comments than you stripped out
I personally think that some descriptions of what you are doing
would be great in teh comments.
ascii art too if needed...
Also some diagrams in any form you want would be nice..
all that about 1000 words and a picture is true.
Thanks,
Jeff
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