real effect.
Optimize vfs_msync(). Avoid having to continually drop and re-obtain
mutexes when scanning the vnode list. Improves looping case by 500%.
Optimize ffs_sync(). Avoid having to continually drop and re-obtain
mutexes when scanning the vnode list. This makes a couple of assumptions,
which I believe are ok, in regards to vnode stability when the mount list
mutex is held. Improves looping case by 500%.
(more optimization work is needed on top of these fixes)
MFC after: 1 week
f883ef447a