Thomas Graf [off-list ref] wrote:

rhashtable currently allows to use a bucket lock per bucket. This
requires multiple levels of complicated nested locking because when
resizing, a single bucket of the smaller table will map to two
buckets in the larger table. So far rhashtable has explicitly locked
both buckets in the larger table.

By excluding the highest bit of the hash from the bucket lock map and
thus only allowing locks to buckets in a ratio of 1:2, the locking
can be simplified a lot without losing the benefits of multiple locks.
Larger tables which benefit from multiple locks will not have a single
lock per bucket anyway.

Signed-off-by: Thomas Graf <tgraf@suug.ch>

Thomas, could you please hold off on these changes? They totally
conflict with my rehash work, which is going to render these changes
moot anyway since it'll completely change how expansion/shrinking
works.

Thanks,
-- 
Email: Herbert Xu [off-list ref]
Home Page: http://gondor.apana.org.au/~herbert/
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