diff options
author | Nathan Lynch <ntl@pobox.com> | 2008-12-23 18:55:54 +0000 |
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committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2009-01-08 16:25:10 +1100 |
commit | 93197a36a9c16a85fb24cf5a8639f7bf9af838a3 (patch) | |
tree | c8f70ac532dd9fa2d1de142994383c108603499a /firmware | |
parent | 5c9a2606bcad101e169012d9f79ab3aed60926aa (diff) |
powerpc: Rewrite sysfs processor cache info code
The current code for providing processor cache information in sysfs
has the following deficiencies:
- several complex functions that are hard to understand
- implicit recursion (cache_desc_release -> kobject_put -> cache_desc_release)
- explicit recursion (create_cache_index_info)
- use of two per-cpu arrays when one would suffice
- duplication of work on systems where CPUs share cache
Also, when I looked at implementing support for a shared_cpu_map
attribute, it was pretty much impossible to handle hotplug without
checking every single online CPU's cache_desc list and fixing things
up... not that this is a hot path, but it would have introduced
O(n^2)-ish behavior during boot. Addressing this involved rethinking
the core data structures used, which didn't lend itself to an
incremental approach.
This implementation maintains a "forest" (potentially more than one
tree) of cache objects which reflects the system's cache topology.
Cache objects are instantiated as needed as CPUs come online. A
per-cpu array is used mainly for sysfs-related bookkeeping; the
objects in the array just point to the appropriate points in the
forest.
This maintains compatibility with the existing code and includes some
enhancements:
- Implement the shared_cpu_map attribute, which is essential for
enabling userspace to discover the system's overall cache topology.
- Use cache-block-size properties if cache-line-size is not available.
I chose to place this implementation in a new file since it would have
roughly doubled the size of sysfs.c, which is already kind of messy.
Signed-off-by: Nathan Lynch <ntl@pobox.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'firmware')
0 files changed, 0 insertions, 0 deletions