struct thread allocation

["Nicolas Thery" <nthery@xxxxxxxxx>]

Hello,

Instances of struct thread are allocated using a custom object caching
mechanism (per-cpu list of free structures (gd_tdffreeq) backed up by
zone).

Why doing so instead of using the objcache or kmalloc?  Was the lwkt
s/system implemented before objcache?

Cheers,
Nicolas