HEADS UP - major structure size changes in HEAD
dillon at apollo.backplane.com
Sun Jun 6 10:55:21 PDT 2010
The recent lwkt_token revamp significantly changes the size of
miscellanious structures in the HEAD branch. A full kernel + modules
recompile is recommended for people tracking HEAD.
These lwkt_token changes will make it a lot easier for us to proceed
on the MPSAFE work. The simplified API makes tokens much easier
to work with now.
The acquisition and release of recursive tokens is also now virtually
free (not even atomic ops are needed), meaning that developers doing
MPSAFE work can acquire a token multiple times in a deep call paths
without having to worry about any loss of performance. This will
make locking up the APIs a lot easier.
We want to use tokens for locking up major system APIs with deep
call paths (e.g. I/O, VM, PMAP, etc) because tokens are not subject
to lock order reversals, so they can be acquired in any order. This
is needed since these major system APIs call each other back and
<dillon at backplane.com>
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